(a) A municipality may not elect to participate in the supplemental disability benefits fund after August 31, 1987.
(b) Each municipality that elected to participate in the supplemental disability benefits fund before September 1, 1987 ceases participation in that fund at midnight on December 31, 1987, and its employees shall cease to be covered for supplemental disability benefits as to any injuries subsequently sustained. Each municipality participating in the supplemental disability fund on December 31, 1987, is entitled to participate in any distributions and transfers authorized by the board of trustees pursuant to Section 855.313.