If a member of a State or local retirement or pension system transfers on or after July 1, 1990, to a State or local retirement or pension system for a police department or fire department, the plans, rules, regulations, guidelines, and policies of the new system govern to determine: the years of service necessary to qualify the member for retirement from the new system; and the years of service and amount of retirement benefits to be credited by the new system for the years of service and retirement benefits earned under the previous system. The determinations made under subsection (a)(2) of this section shall be made by actuarial computations of the new system.