Sec. 1. SCOPE. (a) A retirement system is established by this Act for employees of each municipality having a population of more than 760,000 and less than 860,000.

(b) Any right or privilege accruing to any member of a retirement system established by this Act is a vested right according to the terms of this Act.

(c) This Act continues to apply to a municipality described by Subsection (a) and a retirement system established by this Act continues to operate regardless of any change in the municipality's population.