Notwithstanding the provisions of section 7-473c, if any such municipal employer and any such employee organization are unable to resolve the compensation or exchange of benefits issue after reopening the agreement pursuant to section 7-478c by May 31, 2000, the parties shall submit the issue to the State Board of Mediation and Arbitration, and said board shall make every effort to resolve the issue through mediation not later than June 30, 2000.