California Code, Public Utilities Code - PUC § 130255

(a) If a commuter or urban rail transit system is proposed to serve two or more counties, the commissions in those counties shall form a joint powers entity to conduct plan refinement studies, design, select the technology, determine the cost, locate the routes and access points, and supervise the construction, operation, and management of the system.

(b) The joint powers entity shall designate the operator of the system.

(c) If state funds are to be used for the operation of the system, at least four months prior to implementing service on the system, the joint powers entity shall submit its plan for the operation to the Legislature.