(2) Postretirement adjustments, if any, shall be applied by the respective systems based on the payments made under subsection (1) of this section.
(3) The department shall adopt rules under chapter
34.05 RCW to ensure that where a dual member has service in a system established under chapter
41.32, 41.40, 41.44, 41.35, 41.37, or
43.43 RCW; service in plan 2 of the system established under chapter
41.26 RCW; and service under the city employee retirement system for Seattle, Tacoma, or Spokane, the additional cost incurred as a result of the dual member receiving a benefit under this chapter shall be borne by the retirement system incurring the additional cost.