Senior Secured Interim Term Loan Facility And Senior Unsecured Revolving Credit Facility COMMITMENT LETTER

Exhibit 10.1

DEUTSCHE BANK TRUST COMPANY AMERICAS
60 Wall Street
New York, New York 10005

DEUTSCHE BANK SECURITIES INC.
60 Wall Street
New York, New York 10005

December 21, 2005

Trizec Properties, Inc.
10 S. Riverside Plaza, Suite 1100
Chicago, IL 60606

Senior Secured Interim Term Loan Facility
And
Senior Unsecured Revolving Credit Facility
COMMITMENT L ETTER

Ladies and Gentlemen:

Trizec Properties, Inc. (“Trizec”) has advised Deutsche Bank Trust Company Americas (“DBTCA”) and Deutsche Bank Securities, Inc. (“DBSI” and together with DBTCA, “DB”) (A) that it desires to acquire, through a newly-formed, wholly-owned subsidiary of Trizec (the “Borrower”), for a total consideration of approximately $1.626 billion, a portfolio of thirteen (13) office properties and four (4) entitled sites totaling 7.8 acres of land, all located in southern California (the “Portfolio Acquisition”), from Arden Realty Limited Partnership (“Arden OP”) (in conjunction with the acquisition of Arden Realty Inc. (“Arden”) by General Electric Capital Corporation (“GECC”)) pursuant to (i) a purchase and sale agreement dated as of December 19, 2005 (the “Acquisition Agreement”) between Trizec Holding Operating LLC, a subsidiary of Trizec (“THO”), and GECC, and (ii) a merger agreement (the “Merger Agreement”) among Arden, Arden OP, GECC and certain of its subsidiaries and Trizec and THO, (B) that such Portfolio Acquisition will be accomplished (as contemplated in the Acquisition Agreement and the Merger Agreement) through a qualified intermediary arrangement to facilitate a series of 1031 Exchanges that are contemplated to effect planned asset dispositions subsequent to closing (collectively, the “Transactions”), and (C) that, in connection with the above, Trizec desires to establish a senior secured interim term loan facility of up to $1.475 billion for the Borrower (the “Interim Facility”). The proceeds of the Interim Facility, together with the Equity Investment (as defined below), will be used by the Borrower (i) to finance the Portfolio Acquisition and (ii) to pay closing costs in connection

therewith. You have asked for a financing commitment for the entire amount of the Interim Facility as provided herein. Capitalized terms used in this letter agreement but not defined herein shall have the meanings given them in the summary of terms and conditions of the Interim Facility which is attached as Exhibit A hereto.

Promptly following the public announcement of the Portfolio Acquisition and the Merger Transaction (as defined below), you have requested that DB request the lenders (the “Existing Revolving Facility Lenders”) under Trizec’s existing $750 million revolving credit facility (the “Existing Revolving Facility”) to approve an amendment to the Existing Revolving Facility (the “Existing Revolving Facility Amendment”) which reflects the changes blacklined in the summary of terms and conditions of the Existing Revolving Facility which is attached as Exhibit B hereto. If the Existing Revolving Facility Amendment is approved by the affirmative vote of the Required Lenders (as defined in the Existing Revolving Facility Loan documents), the effectiveness of such amendment will be conditioned upon consummation of the Portfolio Acquisition and the closing of the Interim Facility in accordance with the terms of this Commitment Letter and the Fee Letter. If the Existing Revolving Facility Amendment is not so approved, Trizec desires to establish a replacement $750 million revolving credit facility (the “Replacement Revolving Facility”) on substantially the same terms as those in the Existing Revolving Facility, as amended to reflect the changes shown in Exhibit B hereto. The effectiveness of the Replacement Revolving Facility will be conditioned upon consummation of the Portfolio Acquisition and the closing of the Interim Facility in accordance with the terms of this Commitment Letter and the Fee Letter.

Subject to the terms and conditions described in this Commitment Letter and the summaries of terms and conditions set forth in Exhibits A and B hereto (collectively, together with the Fee Letter referred to below, this “Commitment Letter”), DBTCA is pleased to inform you of its commitment to provide the entire amount of the Interim Facility and the Replacement Revolving Facility (each a “Facility” and together, the “Facilities”).

For purposes of this Commitment Letter, “DB” shall mean DBTCA, DBSI and/or any affiliate thereof as they shall determine to be appropriate to provide the services contemplated herein. Each of DBTCA and DBSI may, in performance of its services under this Commitment Letter, delegate such of its functions as it may select to and/or employ the services of any of its affiliates; provided, however, that no such delegation shall affect the terms hereof. Each of DBTCA and DBSI may allocate, in whole or in part, to such affiliates any fees payable to it in such manner as it may in its sole discretion see fit.

Section 1. Conditions Precedent .

The commitment and all other obligations of DB hereunder with respect to the Facilities are subject to the satisfaction of the following conditions precedent, all as determined by DBTCA:

     (a) the delivery to DBTCA of the final executed Merger Agreement and confirmation by DBTCA that there have been no changes or modifications reflected in the final executed Merger Agreement from the draft thereof attached as Exhibit K to the final executed Acquisition Agreement delivered to DBTCA on December 19, 2005 by Trizec as part of its proposal for the Transactions, that are adverse to the interests of the lenders in any material respect (all references in this Commitment Letter to the Acquisition Agreement or the Merger Agreement are references to the final executed version thereof delivered to and confirmed to be acceptable by DBTCA as provided in this clause (a) and clause (b) below);

     (b) confirmation by DBTCA that there have been no changes or modifications to the final executed Acquisition Agreement delivered to it by Trizec on December 19, 2005 other than any changes or modifications that (i) are required due to changes or modifications to the final executed Merger Agreement that are confirmed to be acceptable by DBTCA as provided in clause (a) above and (ii) are not adverse to the interests of the lenders in any material respect;

     (c) the satisfaction of all conditions precedent to the closing of the Portfolio Acquisition contemplated under the Acquisition Agreement and the concurrent closing of the Portfolio Acquisition and the transactions contemplated by the Merger Transaction;

     (d) the preparation, execution, delivery and effectiveness of loan documentation with respect to the Interim Facility, including, without limitation, a credit agreement, security agreements, guaranties, and other agreements incorporating and substantially consistent with the terms and conditions outlined in this Commitment Letter with respect to the Interim Facility, and with such other terms as may be reasonably satisfactory to DB and its counsel and Trizec and its counsel (the “Interim Facility Operative Documents”);

     (e) the preparation, execution, delivery and effectiveness of loan documentation with respect to the Existing Revolving Facility Amendment or the Replacement Revolving Facility, as applicable, including, without limitation, a credit agreement or credit agreement amendment, guaranties, and other agreements incorporating and substantially consistent with the terms and conditions outlined in this Commitment Letter with respect to the Existing Revolving Facility Amendment or the Replacement Revolving Facility, as applicable, and with such other terms as may be reasonably satisfactory to DB and its counsel and Trizec and its counsel (the “Revolving Facility Operative

Documents” and together with the Interim Facility Operative Documents, the “Facility Operative Documents”);

     (f) Trizec shall make an equity investment in the Borrower of approximately $167 million in order to fund the balance of the purchase price for the Portfolio Acquisition and closing costs in connection therewith;

     (g) since September 30, 2005, after giving effect to the pro-forma condition of Trizec and its affiliates described in the projections delivered to DB on December 20, 2005, there has not been any change, event, condition, development or occurrence that could, in the opinion of DB, have, individually or in the aggregate, a material adverse effect on the business, condition (financial or otherwise), operation or performance of Trizec and its affiliates taken as a whole;

     (h) since the date of the Merger Agreement, there has been no “Material Adverse Effect” (as defined in the Merger Agreement) such that the condition set forth in Section 9.02(e) of the Merger Agreement is not satisfied; and

     (i) the satisfaction of the other conditions precedent to (x) the funding of the Interim Facility contained in Exhibit A hereto and (y) the effectiveness of the Existing Revolving Facility Amendment or the funding of the Replacement Revolving Facility, as applicable, contained in Exhibit B hereto.

Section 2. Commitment Termination .

DB’s commitment hereunder will terminate on the earliest of (a) the date the Facility Operative Documents become effective in accordance with their respective terms and the Transactions have been consummated, (b) the date of the termination of the Acquisition Agreement and the Merger Agreement, (c) June 30, 2006, and (d) December 22, 2005 in the event that Trizec fails on or before 5:00 p.m. (New York City time) on such date (i) to accept the provisions hereof by signing the enclosed copy of this Commitment Letter (including the Fee Letter) and returning them to DB, (ii) to make the initial payment to DB required pursuant to the Fee Letter, (iii) to deliver the final executed Merger Agreement in the form required pursuant to clause (a) of Section 1 hereof and (iv) to deliver the final executed Acquisition Agreement in the form required pursuant to clause (b) of Section 1 hereof. In addition, DB’s commitment hereunder with respect to the Replacement Revolving Facility shall in any event terminate on the effective date of the Existing Revolving Facility Amendment. Each of the parties acknowledges and agrees that the commitment letters dated December 19, 2005 and December 20, 2005 among DB and Trizec are of no further force or effect and are superceded and replaced by this Commitment Letter in all respects.

Section 3. Syndication .

DB reserves the right, prior to or after the execution of the Facility Operative Documents, to syndicate all or a portion of its commitment under each of the Interim Facility and the Replacement Revolving Facility (if applicable) to one or more other financial institutions,

trusts, funds or other entities in consultation with Trizec, that will become parties to the relevant Facility Operative Documents pursuant to a syndication to be managed by DB (the financial institutions, trusts, funds and other entities becoming parties to the Facility Operative Documents with respect to either of the Facilities being collectively referred to herein as the “Lenders”). DB will manage all aspects of the syndication of each of the Facilities in consultation with Trizec, including, without limitation, the timing of all offers to potential Lenders, the determination of the amounts offered to, and selection of, potential Lenders, the acceptance and allocations of commitments of the Lenders and the titles and compensation to be provided to the Lenders under each of the Facilities. The commitment of DBTCA hereunder is not subject to the successful completion of any such syndication.

Trizec agrees to cooperate with DB to assist DB in syndicating the Facilities by (i) making senior management, representatives and advisors of Trizec available to participate in information meetings with potential Lenders under the Facilities at such times and places as mutually agreed; (ii) using its commercially reasonable efforts to ensure that DB’s syndication efforts benefit from Trizec’s lending relationships; (iii) assisting in the preparation of a customary confidential information memorandum for each of the Facilities and other customary marketing and rating agency materials to be used in connection with the syndication of each of the Facilities; (iv) providing DB with all projections, including updated projections, from time to time requested by DB from the date of this Commitment Letter through the successful completion of the syndication of each of the Facilities; and (v) pr