In any case where the Washington state patrol retirement system has in existence an agreement with another retirement system in connection with exchange of service credit or an agreement whereby members can retain service credit in more than one system, an employee holding membership in, or receiving pension benefits under, any retirement plan operated wholly or in part by an agency of the state or political subdivision thereof, or who is by reason of his or her current employment contributing to or otherwise establishing the right to receive benefits from any such retirement plan, shall be allowed membership rights should the agreement so provide.