I'm interested to see how this turns out when its been chernobalized. I would have figured the best way to achieve that type of effect ( atleast for a still shot) would be to do a paint over in Photoshop, ya know, Channel your Inner Dylan Cole, or Alp Altnair, something like that. I can think of a few ways though to model in a busted wall. Basically involved all cutting and slicing poly's deleting faces you dont want, filling holes and appending to poly where and there. Normal modeling, Keep it clean then perhaps use Disp or Normal maps to give it some definition,
Or you could Do the Zbrush trick, model it in maya, as just general basic shapes, busted walls ect...then take it to Z and subdivide some, then Just layer several passes of destruction on it with random brushes that have nice crack like effects in them..

Not necessarily a big Z knowledge base by any means, but i know alot of people have used it for a weathered and destroyed environment effect.

G-man