A waiver issued under section §20.437 of this title (relating to Waiver of Vehicles to Meet Required Fleet Percentages) shall be kept on file by the comptroller for two years from date of issuance. A valid, current waiver on file for a state agency shall be deemed sufficient basis for a waiver of the purchasing restrictions for state agencies which are set forth in §20.235 of this title (relating to Purchase of Motor Vehicles).