In the event any protective device is to be installed or altered at an existing or relocated crossing or any reconstruction or alteration is made at an existing separation structure, with the aid of any federal funds administered by the Federal Highway Administration of the United States Department of Transportation, the Oregon Department of Transportation shall, unless the parties agree otherwise:
(1) Apportion the amount of such federal funds to payment of installation, reconstruction, or alteration costs; and(2) Apportion the remaining costs of installation, reconstruction, alteration, and maintenance as provided by ORS 824.238 and 824.242 to 824.248; however, in a case where the federal fund assistance equals or exceeds 75 percent of the cost of installing, altering and reconstructing protective devices at an existing or relocated crossing, the remaining costs, except for maintenance costs, may be allocated entirely to the Grade Crossing Protection Account.