(a) If the electric utility facilities financed, acquired, constructed, or completed are a part of a utility system of a political subdivision, the obligation to make the contract payments to acquire an ownership interest is a lien on the revenue of the system on a parity with the outstanding bonds of the system to the extent permitted in the ordinance or resolution authorizing or the deed of trust or indenture securing the payment of the outstanding bonds.
(b) If the ordinance or resolution authorizing or the deed of trust or trust indenture securing the revenue bonds of a utility system provides for the subsequent issuance of additional bonds or the creation of a contractual obligation described by Section 164.004 and provides that the payments to be made for the security or payment of the subsequent bonds or contractual obligation are to be on a parity with the previously issued bonds or bonds then to be issued, the political subdivision may, subject to any conditions contained in that ordinance, resolution, deed of trust, or trust indenture, authorize, issue, and sell additional bonds or incur the contractual obligation in a different series payable from the entire revenue of the utility system on a parity with the previously issued bonds or bonds then to be issued and secured by a lien on the revenue of the system on a parity with the lien securing the previously issued bonds or bonds then to be issued. This subsection applies without regard to whether the previously issued bonds:
(1) were issued before August 29, 1977; or
(2) are an original issue or a refunding issue.

(c) A political subdivision may pledge the revenue of a utility system to pay contract payments to acquire an ownership interest in an electric utility facility under this chapter.
(d) In this section, “utility system” includes a combined utility system.