Where the board's final decision and order makes a determination of invalidity, and the city or county subject to the order has not yet enacted legislation in response to the board's order, the city or county may file a motion to clarify, modify or rescind invalidity. The motion and any response may be supported by evidence arising subsequent to adoption of the invalidated legislation. Pursuant to RCW 36.70A.302(6), the board shall expeditiously schedule a hearing on the motion. Not later than thirty days after the hearing on the motion, the board shall issue any supplemental order continuing, clarifying, modifying or rescinding invalidity based on information provided at the hearing.