[gordon]

Looks to me that they are building up the chassis furthest away from the camera, robbing parts from the others. Presumption would be that the one visible cab would go on that. Number of steering sheels on the wall roughly matches the number of chassis, almost suggesting we are not seeing part of a larger operation with more trucks scattered about.

Consider what we are NOT seeing; no body parts, running boards, fuel tanks that I can see, no obvious burning (as if the fuel tanks had gone up) so I'd think mechanical damage.

Notice that things like the bumperettes and tow hitch have been stripped from the left chassis, and you'd have to be really keen to do that, even on a new truck. Such parts would almost never get damaged in a purely mechanical incident such as a building collapse.