(a) Notwithstanding any other provision of this part, a contracting agency and its employees may agree, in writing, to share the costs of any optional benefit that is inapplicable to a contracting agency until the agency elects to be subject to the benefit. The agreement shall specify the exact percentage of member compensation that shall be paid toward the current service cost of the benefits by members. The member contributions shall be normal contributions over and above normal contributions otherwise required by this part and shall be treated as normal contributions for all purposes of this part. The contributions shall be uniform with respect to all members within each of the following classifications: local miscellaneous members, local police officers, local firefighters, county peace officers, and all local safety members other than local police officers, local firefighters, and county peace officers. The balance of any costs shall be paid by the contracting agency and shall be credited to the employer’s account.
(b) This section shall not apply to any optional benefit that is elected by a contracting agency prior to January 1, 1979.
(c) This section shall not apply to any contracting agency nor to the employees of a contracting agency until the agency elects to be subject to this section by contract or by amendment to its contract made in the manner prescribed for approval of contracts. Contributions provided by this section shall be withheld from member compensation or otherwise collected when the contract amendment becomes effective.
(d) For the purposes of this section, all contributions, liabilities, actuarial interest rates, and other valuation factors shall be determined on the basis of actuarial assumptions and methods that, in the aggregate, are reasonable and which, in combination, offer the actuary’s best estimate of anticipated experience under this system.
(e) The additional employer contributions required under this section shall be computed as a level percentage of member compensation. The additional contribution rate required at the time this section is added to a contract shall not be less than the sum of (1) the actuarial normal cost, plus (2) the additional contribution required to amortize the increase in accrued liability attributable to benefits elected under this section over a period of not more than 30 years from the date this section becomes effective in the public agency’s contract.
(f) Nothing in this section shall preclude a contracting agency and its employees from independently agreeing in a memorandum of understanding to share the costs of any optional benefit or when initially entering into a contract, any benefit, in a manner inconsistent with this section. However, any agreement in a memorandum of understanding that is inconsistent with this section shall not be part of the contract between this system and the contracting agency.