If Thomas runs on New York subway system in the 80s

interesting.  this rolling stock belongs to Canadian Pacific I think.  Security around rail yards must be very lax.  It will take many hours to complete this mural.

More than likely, the mural was painted while this was in a storage siding somewhere in Podunk. Security around major rail facilities is pretty tight, at least in the US. Some smaller and/or older yards are pretty accessible though. But many cars are stored on unused branch lines and sidings or leased space on short lines, sometimes for months or even years. It gives the taggers and mural artists plenty of time to work unobserved. This particular car is a grain hopper, so I imagine it gets used seasonally and is left stored in the off season.

Does that say 'Grave' or 'Crave'?

I’m gonna say “Crave”. I had to enlarge the image and study it for a bit because I couldn’t tell either.