I can't see any evidence of frame damage in the pics...albeit the pass. side spring hanger/shackle is obviously pushed up and foward...
If the part of the frame that the shackle hangs from is bent, its probably minor, and is typically not a big problem to repair.
If the shackle hanger itself is all that's damaged, that's also a reasonably simple repair.
The leaf spring may be over arched, and/or the clamps may be spread, etc....make sure the spring set up is ok, including the forward hanger that is not pictured, as the force involved would be transmitted to the front of the spring, etc.
This is a great time to think about getting a Shrock rear bumper....as the other party's insurance will settle, and just write you a check...you can simply get a real steel bumper instead of the easily dented thin stock bumper.
The next time you are rear ended, you can smile and drive away unscathed.