Mu26aeh: I've seen a few other full-car artworks like that, and like that one, the best artist/vandals recognize that the reporting marks and data HAVE to be readable. For art like that, I think it would be good advertizing for the railroads to give the artists permission, and a place to work, even if it was just a blue-flagged siding. It doesn't hurt the car, it doesn't cost the railroad anything, and it does get the public's attention.
Unfortunately, most freight car "art" doesn't make the car look better, doesn't help the railroad's image, and costs money to restencil the painted-over data.