(a) A written agreement under this subchapter between a public employer and the fire fighters association recognized as the sole and exclusive bargaining agent supersedes a previous statute concerning wages, salaries, rates of pay, hours of work, and other terms and conditions of employment to the extent of any conflict with the previous statute.
(b) A written agreement under this subchapter preempts all contrary local ordinances, executive orders, legislation, or rules adopted by the state or a political subdivision or agent of the state, such as a personnel board, a civil service commission, or a home-rule municipality.

(c) An agreement under this subchapter may not diminish or qualify any right, benefit, or privilege of an employee under this chapter or other law unless approved by a majority of the votes received in a secret ballot referendum of the members of the fire fighters association recognized as the sole and exclusive bargaining agent.