Notwithstanding the provisions of the Government Code, employees of the district may authorize and, upon such authorization, the district shall make deductions from wages and salaries of such employees:
(a) Pursuant to a collective bargaining agreement with a duly designated or certified labor organization for the payment of union dues, fees, or assessments.
(b) For the payment of contributions pursuant to any health and welfare plan or pension or retirement plan.
(c) For any purpose for which deductions may be authorized by employees of any private employer.