I see more and more (Mainly RR tankers & hoppers cars) in our rail yard that are filthy.
Instead on cleaning the car someone will wipe off the parts where the lettering and number info is dirty so you can read it.
A lot of trains roll by real slow in the switching yard outside the rail yard all kinds of cars Box,garbage,hoppers and flatbeds
Where the graffiti covers the info the RR will just spray paint a square over the graffiti and stencil new info over it.
I have also noticed that a lot of graffiti painters now make sure that they don't cover the info numbers and lettering.
They graffiti around them so their work does not get painted over.
Nice people they are.