Ariz. Rev. Stat. § 40-1125
An authority may cooperate with and enter into agreements with the state of Arizona or any public agency for the acquisition, construction, improvement, completion, maintenance, operation or repair, joint or otherwise, and in whole or in part, of public transportation facilities and equipment, and for study and planning thereof. In connection with any such cooperation or contract, the state or any public agency may make public contributions to the authority as in the judgment of the legislature, or the governing board of the agency, are necessary or proper for its undertaking, and the authority may reimburse the state or public agency for any such advance or contribution from the proceeds of the sale of bonds or any other funds available to the authority. The state or any public agency may also authorize, aid and assist the authority to carry out any activity which the state or public agency is by law authorized to perform and carry out in its own behalf.
A.R.S. § 40-1125