(a) Notwithstanding Section 20484, a contracting agency that continued the local system for members who elected to become members of this system prospectively pursuant to Section 20504 may transfer to this system the cash and securities to the credit of the local system and held on account of persons who became members of this system. The transfer of cash and securities shall be made pursuant to Section 20530. The service credited under the local system shall be credited under this system as prior service.
(b) This section shall not apply to the employees of any contracting agency nor to any contracting agency unless and until the contracting agency elects to be subject to this section by amendment to its contract with the board, made pursuant to Section 20474.