"Public service" with respect to a local member also means service rendered to a public agency if that agency or a function of that agency is assumed by a contracting agency or a public agency that thereafter becomes a contracting agency.
This section shall not apply to any contracting agency nor to the employees of any contracting agency until the agency elects to be subject to this section by contract or by amendment to its contract made in the manner prescribed for approval of contracts.
Ca. Gov. Code § 21025