AMENDMENT OF LEASE

Exhibit 10.1

AMENDMENT OF LEASE

AGREEMENT dated as of the 26 ^th day of May, 2009 by and between 60 HUDSON OWNER LLC (successor to Westport Communications, LLC and Hudson Telegraph Associates, L.P., formerly known as Hudson Telegraph Associates), a Delaware limited liability company, having an office c/o FirstService Williams LLC, 380 Madison Avenue, New York, New York 10017 (“Landlord”), and FIBERNET EQUAL ACCESS, LLC , a New York limited liability company, having an address at 220 West 42 ^nd Street, , New York, New York 10036 (“Tenant”).

W I T N E S S E T H :

WHEREAS , Landlord and Tenant are the present parties to an agreement of lease, dated as of April 1, 2001 (“Original Lease”), as heretofore amended on numerous occasions (collectively, “Existing Lease”), pursuant to which Landlord now leases to Tenant and Tenant now leases from Landlord portions of the ground floor (“Ground Floor Space”) and basement (“Basement Space”), as more particularly described in the Existing Lease, the Ground Floor Space and the Basement Space sometimes hereinafter collectively called the “Existing Space,” in Landlord’s building known as 60 Hudson Street, New York, New York (“Building”); and

WHEREAS , Landlord and Tenant also are the present parties to an agreement of lease, dated as of February 17, 1998, as heretofore amended on numerous occasions (collectively, the “19/12 Lease”), pursuant to which Landlord now leases to Tenant and Tenant now leases from Landlord, portions of the 19 ^th , 12 ^th and ground floors and the lower mezzanine in the Building, as more particularly described in the 19/12 Lease; and

WHEREAS , Landlord and Tenant wish to (i) extend the Term (“Extension Term”) of the Existing Lease so as to expire on July 31, 2022 (“New Expiration Date”), (ii) modify and amplify the Existing Lease in certain other respects, and (iii) provide for certain acknowledgments and consents with respect to the Existing Lease and the 19/12 Lease, all upon and subject to the terms and conditions hereinafter set forth; and

WHEREAS, Tenant and Zayo Group, LLC (“Zayo”) have advised Landlord that, on or about the date hereof, they are entering into a document called an Agreement and Plan of Merger with respect to Zayo’s proposed acquisition of the stock of FiberNet Telecom Group, Inc. (“FTG”), which proposed acquisition is sometimes hereinafter referred to as the “Proposed Transfer.”

NOW, THEREFORE , in consideration of the foregoing and the mutual covenants hereinafter contained, Landlord and Tenant agree that the Existing Lease hereby is further amended as follows:

1. Definitions . All terms contained in this Agreement shall, for the purposes hereof, have the same meanings ascribed to them in the Existing Lease unless otherwise defined herein. As used herein, the term “Extended Lease” shall mean the Existing Lease as amended by this Agreement and as the same may be hereafter amended.

2. Extension Term .

(A) The Extension Term shall commence on January 1, 2016 and expire on the New Expiration Date, unless sooner terminated as provided in the Extended Lease.

(B) During the Extension Term:

(i) All currently applicable terms and conditions of the Existing Lease, as further amended hereby, shall be applicable to and govern the continued leasing of the Existing Space.

(ii) The Existing Space shall be leased to Tenant in its “as is” condition on December 31, 2015 and Landlord shall not be required to perform any work or provide any work allowance to prepare either the Ground Floor Space and/or the Basement Space for Tenant’s continued occupancy.

(C) Tenant’s continued occupancy of the Existing Space from and after December 31, 2015 shall constitute its acknowledgement that, on December 31, 2015, the Existing Space and the Building were in good and satisfactory condition.

3. Amounts Payable by Tenant During the Extension Term .

(A) Effective as of January 1, 2016, Fixed Rent for the Ground Floor Space (which includes an annual cumulative two and one-half (2-  ¹ / 2 %) percent increase intended to reimburse Landlord for anticipated increases in Building operating expenses in lieu of operating expense, porters’ wage and/or utility expense escalation provisions) shall be changed to be as set forth in the following table:

(B) Fixed Rent for the Basement Space is not included in the table in subparagraph (A) and shall remain as set forth in Article 76 of the Existing Lease.

(C) The Fixed Rent payable pursuant to subparagraphs (A) and (B) hereinabove does not include the supplementary charges set forth in the Existing Lease (including, without limitation, tax escalation charges, electricity charges, Percentage Rent and Transport Fee Rent), all of which supplementary charges shall continue to remain payable as and when provided in the applicable provisions of the Existing Lease. There is to be no rent concession during the Extension Term.

4. Modification of Landlord’s Special Termination Rights . The first sentence of subsection (A), the entire subsections (B), (C), (E), (F) and (G) of Section 72 and the entire Section 57 of the Original Lease (all to the extent still remaining applicable) shall be deleted and superseded by the following provisions:

“In the event that (a) twice in any twelve (12) consecutive monthly period, Tenant shall default in the payment of Fixed Rent or additional rent or any part of either and such default shall have continued after Landlord shall have notified Tenant thereof and the applicable grace period shall have expired, then, notwithstanding that any such default may have been cured at any time after the expiration of the applicable grace period, any further

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default by Tenant of such nature within such twelve (12) consecutive monthly period shall be deemed a violation of a substantial obligation of the Extended Lease; or (b) if Landlord, acting in good faith, determines that Tenant’s business operations within the Building are either inappropriate for, or being conducted in a manner which is detrimental to, the Building, Landlord notifies Tenant in writing of such determination and, in such notice, specifies in reasonable detail the business operations of Tenant which Landlord, acting in good faith, has determined are either inappropriate for, or being conducted in a manner which is detrimental to, the Building (Landlord hereby acknowledging that (i) Tenant’s business operations within the Building, as they are presently being conducted, presently are appropriate for, and presently are being conducted in a manner which is not detrimental to, the Building, and (ii) any future such operations which are conducted in the same manner, except for modifications necessary to conform to then prevailing telecommunication and/or collocation industry practices and technology, shall not be considered inappropriate for, or detrimental to, the Building), and Tenant, within thirty (30) days after Landlord sends such notice, fails to discontinue or modify such business operations in a manner so that Landlord, acting in good faith, can no longer make such determination, then such failure by Tenant to discontinue or modify such business operations shall also be deemed to be a violation of a substantial obligation of the Extended Lease. In the event of an occurrence of an event set forth in subparagraph (a) or (b) above which constitutes a violation of a substantial obligation of the Extended Lease, Landlord may serve a written twenty (20) day notice of cancellation of the Extended Lease (“Cancellation Notice”) and the Term of the Extended Lease thereupon shall end and expire, as fully and completely as if the expiration of such twenty (20) day period were the day herein definitively fixed for the date of natural expiration of the Extended Lease and its Term, and Tenant shall quit and surrender to Landlord the entire premises then covered by the Extended Lease, but Tenant shall remain liable as elsewhere provided in the Extended Lease. Without limiting the generality of the foregoing, no provision hereof shall affect Landlord’s rights of termination and resultant remedies available elsewhere under the Existing Lease (including, without limitation, those set forth in Articles 9, 10, 17 and 18).

If and when Landlord sends a Cancellation Notice, it may, at any time thereafter (even prior to recovering vacant possession of the premises then demised (“Then Premises”) by the Extended Lease by a decision of a court of competent jurisdiction or otherwise pursuant to the provisions of the Extended Lease or applicable law), appoint a Manager of the Then Premises to supervise, manage and conduct the business operations in and about the Then Premises (“Landlord’s Manager”). Landlord’s Manager shall have the full authority (without being subject to any rights of, or obligation to consult with, Tenant or any parent, subsidiary or affiliated party or parties of Tenant) to make and implement all decisions necessary and appropriate so that business operations in and about the Existing Space shall be conducted in a manner consistent with the provisions of Article 66 of the Original Lease and then prevailing telecommunications and/or collocation practices and technology.

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In addition, if and when Landlord sends a Cancellation Notice, Tenant agrees that (i) all items which constitute permanent leasehold improvements in and to the Existing Lease have been, presently constitute and will remain Landlord’s property and Landlord may continue to own and utilize the same without restriction, and (ii) Landlord may, without charge and without liability or accountability of any nature, continue to utilize all equipment utilized in any way in the business operations being conducted in the Then Premises (including, without limitation, Internal MMR Equipment and External MMR Equipment) and receive all monies thereafter payable under all Meet-Me-Room Licenses (including, without limitation, Meet-Me-Room Fees), both for so long as Landlord determines, in its sole and absolute discretion.”

5. Tenant’s Leasing Restrictions .

(A) As an inducement to Landlord to extend the Term for the Extended Lease and to modify certain of Landlord’s termination rights under the Existing Lease, Tenant agrees that its right to lease space in the New York Metropolitan Area (including, without limitation, the five boroughs of New York City, Nassau, Suffolk and Westchester Counties, Eastern New Jersey and southern Connecticut) shall be limited as hereinafter provided for the period from the date of this Agreement through December 31, 2015 (“Restriction Period”). Tenant recognizes and acknowledges that the limitations on its leasing rights hereinafter set forth are a material inducement to Landlord’s willingness to enter into this Agreement and that, accordingly, Landlord shall have all the rights and remedies provided for under the Extended Lease and by Law (including, without limitation, the right of termination set forth in the Extended Lease and the right of injunction) in the event that Tenant fails to or threatens to fail to comply with such limitations.

(B) During the period from the date hereof through and including December 31, 2015 (or any earlier date of termination of the Extended Lease), Tenant shall not lease or propose to lease space in the New York Metropolitan Area, other than (i) existing collocation space currently operated by Tenant or a current affiliate, (ii) space not exceeding 500 rentable square feet at each of not more than five separate locations, to be used solely for incidental services in support of Tenant’s end-user customers in Tenant’s delivery of telecommunication services in the ordinary course of its business, or (iii) solely for the purpose of executive office use (collectively, “Restricted Purposes”), unless and until Tenant shall first have leased directly from Landlord (to the extent Landlord has sufficiently sized space which is at or above ground level then available or to become available within five (5) months following the Tenant making such request) a total of an additional 25,000 rentable square feet of space in the Building (which rentable square footage shall be calculated on the basis of Landlord’s then standard measurement of rentable square footage from time to time in effect during the foregoing period), upon and subject to the following terms and conditions:

(i) Such possible leasing of 25,000 rentable square feet of space in the Building may be accomplished in one or more blocks of space. On any occasion during the Restriction Period when Tenant is considering leasing space in the New York Metropolitan Area for a Restricted Purpose, Tenant shall advise Landlord of such consideration and advise Landlord of the approximate size of space in the Building (which requirements may include minimum size requirements of such blocks) which would satisfy such consideration to enable Landlord to

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reasonably determine the space in the Building which it will lease to Tenant for such purpose and upon and subject to the terms and conditions hereinafter set forth. Any Restricted Leased Space shall have an electrical capacity of 50 watts per rentable square foot (with Tenant to pay Landlord, upon the effectiveness of the leasing of any Restricted Lease Space, for 35 watts per rentable square foot at Landlord’s Standard Building rate in effect at the time the leasing of each applicable Restricted Lease Space commences) and be interconnectable, in accordance with applicable requirements and charges set forth in the Extended Lease, with at least one of Tenant’s other locations within the Building. The size of such space (“Space Dimensions”) shall be determined by Landlord and accepted by Tenant, both acting reasonably. Each block of space so leased by Landlord to Tenant is hereinafter called a “Restricted Leased Space.”

(ii) Except as otherwise hereafter provided, each Restricted Leased Space shall be leased by Landlord to Tenant upon and subject to all currently applicable terms and conditions of the Extended Lease for the Ground Floor Space. Promptly after the Space Dimensions are determined, Landlord and Tenant shall execute and exchange an agreement, consistent with the provisions of this Paragraph 5 and otherwise reasonably satisfactory to Landlord and Tenant, confirming such leasing (“Expansion Agreement”).

(iii) The commencement date of the leasing of any Restricted Leased Space (“Restricted Commencement Date”) shall be the date that the Expansion Agreement is executed and exchanged, any required third party consent(s) thereto specified in the Expansion Agreement have been obtained and Landlord delivers to Tenant vacant possession of the applicable Restricted Leased Space, free of any personal property of the prior occupant thereof and otherwise in its then “as is” condition, except that, if the initial Fixed Rent for the leasing of any Restricted Lease Space remains undetermined when the Expansion Agreement is otherwise ready for execution and exchange, the Expansion Agreement shall be executed and exchanged and include a provision that the Fixed Rent for the applicable Restricted Lease Space shall be determined and (if and to the extent that the provisions of subsection (iv)(d) below are applicable, payable) as provided in subsection (iv) below and the Restricted Commencement Date for such lease shall be the Negotiation Commencement Date (as hereinafter defined). The expiration date of any leasing of any Restricted Leased Space shall be on the New Expiration Date.

(iv) The initial Fixed Rent for any Restricted Leased Space shall be the fair market rental value of such Restricted Leased Space as of such Restricted Commencement Date, based upon the criteria set forth in subsection (c) of this Section (iv) (the “FMRV”), and determined as follows:

(a) Beginning on the date that the Space Dimensions of the applicable Restricted Leased Space are determined (“Negotiation Commencement Date”), Landlord and Tenant shall negotiate in good faith to agree upon the FMRV. If Landlord and Tenant cannot reach agreement within ten (10) business days after the commencement of such negotiations, Landlord and Tenant shall each, within seven (7) business days after the expiration of such ten (10) business day period, select a reputable, qualified, licensed real estate broker having an office in New York County and familiar with the rentals then being charged in the Building for the type of space represented by the applicable Restricted Leased Space (such brokers are referred to herein, respectively, as “Landlord’s Broker” and “Tenant’s Broker”). Landlord’s Broker and Tenant’s Broker shall confer promptly after their selection by Landlord and Tenant and shall negotiate in good faith to agree upon the FMRV. If Landlord’s Broker and Tenant’s Broker cannot reach agreement by the date that is fifteen (15) business days after their designation, then, no later than ten

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(10) business days after the expiration of such fifteen (15) business day period, they shall designate a third reputable, qualified, licensed real estate broker having an office in New York County and familiar with the rentals then being charged in the Building for the type of space represented by the applicable Restricted Leased Space (the “Independent Broker”). Upon the failure of Landlord’s Broker and Tenant’s Broker timely to agree upon the designation of the Independent Broker, the Independent Broker shall be appointed by a Justice of the Supreme Court of the State of New York upon ten (10) days notice, or by any other court in New York County having jurisdiction and exercising functions similar to those exercised by the