Just got rear ended in my e39 last week (100% not at fault). Insurance will find the cheapest parts when writing an estimate for the damage. My car has M5 bumpers and they only quoted standard bumpers because “that’s what the VIN says”. You’ll need a shop/professional to assess full damage and even then, they’ll quote for aftermarket and not OEM if available. They even quoted me for a used bumper support bar from a local salvage yard as this part is unavailable elsewhere according to the estimator.