when an x5 is rear ended, most of the time, all the exhaust hangers are bent forward. you can just tell by looking at the hangers, both exhaust manifold are bent(shifted forward 1-2"). The battery box is another item to check as it often becomes cracked. Remove the rear diffuser(3 phillips screws) and check battery box, while you are there, the 2 inner exhaust hangers for the rear mufflers will need to be checked, the metal brackets for these hangers should have a clearance about 4-5mm between the battery box. Since you are not equipped with a tow bar, the bumper shocks will most likely need to be replaced. If the RHS exhaust is pushed in far enough, it can contact the rear subframe and rear sway bar. So let me break it down for you to check yourself. If your air bag light is on also, i would check the POS battery cable in the trunk. and if there were any passengers wearing their seat belts, then i would check the front seat belt tensioners for triggering. If your car is equipped with Navigation, then the Navigation drive will need to be checked and the BM54 radio checked for proper operation.

Mechanical Repairs

Exhaust Manifolds x2
Exhaust Hangers x4
Right Exhaust Muffler x1
Battery Box x1
Bumper Shocks x2
Bumper Support Clips Upper and Lower x2
Bumper Re-inforcement Bar x1
Rear Diffuser x1
Rear Subframe Carrier x1
Rear Sway Bar x1
Battery Cable Repair kit x1
Drivers/Passenger Seat Belt Tensioner x2
BM54 Radio x1
Nav Computer x1

Body Shop Repairs

Pull Rear End to become straight
Refinish Rear Bumper
Alignment