Hi Joe,
Those are part of a pedestrian overpass. I'm not sure of the origin since I got it in pieces in a junk box (er, I mean treasure chest ) of parts at a show. It may be a Bachmann Plasticville.
I've come across a couple of these in similar shape, but not a complete kit. As you say, has lots of potential uses, so it's something to keep an eye out for.
Jim