The obligation of the district to bargain in good faith with a duly designated or certified labor organization and to execute a written collective bargaining agreement with such labor organization covering the wages, hours and working conditions of the employees represented by such labor organization in an appropriate unit, and to comply with the terms thereof shall not be limited or restricted by the provisions of the Government Code or other laws or statutes and the obligation of the district to bargain collectively shall extend to all subjects of collective bargaining which are or may be proper subjects of collective bargaining with a private employer, including
retroactive provisions. Notwithstanding the provisions of the Government Code or other laws or statutes, the district shall make deductions from wages and salaries of its employees upon receipt of authorization therefor for the payment of union dues, fees or assessments, for the payment of contributions pursuant to any health and welfare plan or pension plan or for any other purpose for which deductions may be authorized by employees of any private employer, where such deductions are pursuant to a collective bargaining agreement with a duly designated or certified labor organization.