Any public official authorized to disburse funds in payment of salaries and wages of public transportation employees may, upon written request of the employee, deduct from the salary or wages of the employee, contributions for payment of voluntary deductions for political action committees sponsored by labor or employee organizations with public transportation employees as members. For the purposes of this section, "public transportation employees" means employees of a public transportation system specified in RCW 35.58.272 who are covered by a collective bargaining agreement.