How it works is it doesn't work. Just now downloaded it, what you're looking at there is an old 2.0 paintshed skin. The idea behind those was a "master" mesh that was aliased from the model, but at some point they decided to dump the whole aliased paintshed thing, probably due to performance issues. Looking at the KUID table for that one, one of the dependencies is;
50ft 2door boxcar,<kuid:-10:197>
That's where the mesh is it's looking for.
Two options if you want that particular boxcar and skin;
1. Clone the original 50ft 2door boxcar,<kuid:-10:197> and run that through the Images2TGA and PM2IM process, and open in content creator to update to 2.9. Then steal the skin from the CP_200068_(LARS),<kuid:87907:15102> and replace the original white skin in your clone with the CP skin.
2. Steal the folders and mesh from 50ft 2door boxcar,<kuid:-10:197> and pop it into what you have now, making a backup copy of the CP skin first, then copying that back in.