(a) A public employer shall not provide to a public employee who is elected or appointed, a trustee, excluded from collective bargaining, exempt from civil service, or a manager any vesting schedule for the employer contribution payable for postretirement health benefits that is more advantageous than that provided generally to other public employees, including represented employees, of the same public employer who are in related retirement membership classifications.
(b) This section shall not require an employer to change the vesting schedule for the employer contribution payable for postretirement health benefits of any public employee who was subject to a specific vesting schedule pursuant to statute, collective bargaining agreement, or resolution for these employer contributions prior to January 1, 2013, or who had a contractual agreement with an employer prior to January 1, 2013, for a specific vesting schedule for these employer contributions.