The general assembly hereby finds and declares that moneys made available for regional transportation systems pursuant to this part 6 shall not be used to supplant existing or budgeted department of transportation funding of any portion of the state highway system within the territory of any authority or any transportation planning region, as defined in section 43-1-1102 (8), that includes any portion of the territory of the authority except as described in detail in an intergovernmental agreement entered into pursuant to section 43-4-603 (1.5).