Update to my post from yesterday, with more pictures.
They're definitely rail related, they have writing saying "Do not hump" (hehe) and "no running board".
So, any other ideas now? Certainly rail related, but they don't have trucks or couplers (at least not attached). They certainly articulate up/down as you can see in the fourth picture. They do have hydraulic lines as well as an air line, but I don't see a brake wheel. I'm not sure what good the air line is without brakes, but maybe it's to run something else, or just to pass it through to other cars behind it? The hydraulic line labels are emergency operator return, emergency operator pressure, I.C.H. and I.C.I.
There are hatches on the tops, with ladders that go down in (one hatch has the cover removed) but there's nothing inside but hoses and lines and stuff. There are bulldozer tracks around, so they were pushed to where they lie.