Every piece of the car has a part number, if they didn't list the modings, diffuser, mounting hardware and towing clevis cover, I wouldn't assume that anything is included. You should call them and verify before making the purchase.
WTH does "remanufactured" mean when referring to a bumper??? (see the link).
I'd pretty much guarantee that it's the rear bumper cover only, with no trim or any other accessories. If it's not remanufactured- it's probably one of those cheap aftermarket pieces- not necessarily horrible, but the quality of the pieces I've seen is less than great......