Cal. Gov. Code § 20479.5

Notwithstanding Section 20479, where a memorandum of understanding entered prior to August 11, 1988, provided a different retirement benefit formula for a subgroup of employees in a member classification, that contracting agency may, pursuant to a memorandum of understanding, amend its contract to provide the same retirement formula applicable to that subgroup to all or part of the contracting agency’s other employees in the same member classification.