Notwithstanding any of the provisions of RCW 81.53.090, where the cost of constructing an overpass or underpass which is part of the state highway system has been paid for in whole or in part by the use of federal funds, the state shall at its expense maintain the entire overpass structure and the approaches thereto, and the railroad company shall at its expense maintain the entire underpass structure, including the approaches thereto. The state shall at its expense maintain the roadway, and the railroad company shall at its expense maintain its roadbed and tracks on or under all such structures.