Any board, agency, organization, or association which participates in the Teachers’ Retirement System of Alabama, but whose employees are not included in the definition of employee in Section 16-25A-1 may, by resolution legally adopted to conform to rules prescribed by the board and upon a majority vote of its employees, elect to have its employees and under certain conditions its retired employees covered by the provisions of this article, provided such board, agency, organization, or association shall contract to pay the full cost of coverage for each such employee in the amounts set forth by the board and as defined in Section 16-25A-1 for a full-time employee; participation, once elected, is irrevocable. Each retired employee shall be given the option to participate under the provisions of Section 16-25A-8(c) provided any employer electing to have its employees covered by this section, shall contribute on account of each of its retired employees an amount equal to any amount appropriated by the state to fund benefits for retired employees. The board shall develop rules and regulations governing the operation of this section which shall contain but not be limited to entry and withdrawal from the plan.