The Commission and an employee organization certified as exclusive representative of a bargaining unit shall execute a collective bargaining agreement incorporating all matters agreed. If a collective bargaining agreement provides for a grievance procedure, that grievance procedure shall be the sole procedure for employees in the bargaining unit. The collective bargaining agreement may include an agency shop or other union security provision. The collective bargaining agreement supersedes any conflicting regulation or administrative policy of the Commission. A single–year or multiple–year collective bargaining agreement shall expire at the close of the appropriate fiscal year. Except as provided in paragraph (2) of this subsection, a collective bargaining agreement shall be effective on the approval of the Commission and the membership of the employee organization representing the bargaining unit. The economic requirements of a collective bargaining agreement shall be effective on approval by the Montgomery County Council and Prince George’s County Council.