Pub. Util. Code, § 30940

The district shall have power to purchase equipment such as cars, trolley buses and motorbuses, rolling equipment, and may execute agreements, leases and equipment trust certificates in the forms customarily used by private corporations engaged in the rapid transit business appropriate to effect such purchase and leasing of rolling equipment and may dispose of such equipment trust certificates upon such terms and conditions as the board may deem appropriate. All money required to be paid by the district under the provisions of such agreements, leases and equipment trust certificates shall be payable solely from the revenue or income to be derived from the transportation system and from grants or loans, or both, as provided in Sections 30701, 30702, and 30703 of this part. Payment for such equipment, or rentals therefor, may be made in installments, and the deferred installments may be evidenced by equipment trust certificates payable solely from such revenue, income, grants, or loans, and title to such equipment shall not vest in the district until the equipment trust certificates are paid.