California Code, Public Utilities Code - PUC § 130109

(a) Except as otherwise provided in subdivision (b), the commission shall enter into a contract with the Board of Administration of the Public Employees' Retirement System, and the board shall enter into that contract, to include all of the employees of the commission into that retirement system, and the employees shall be entitled to substantially similar health benefits as are state employees pursuant to Part 5 (commencing with Section 22750) of Division 5 of Title 2 of the Government Code.

(b) For purposes of providing retirement benefits, the commission may contract with the retirement system that the employees of the county in which the commission is located are members of in lieu of contracting with the board.

(c) Each person employed by the Orange County Transportation Commission on January 1, 1992, may, no later than February 1, 1992, elect to either remain a member of the Public Employees' Retirement System or become a member of the Orange County Employees Retirement System.  All persons who become employed by the commission after February 1, 1991, shall be members of the Orange County Employees Retirement System.