Honestly, there is a reason why the car couldn't sell as a CPO. Yes, CPO cars can have a history of accidents. I'm not sure how severe the accident have to be before it cannot be CPO'ed. However, it seems to me that body structure inspections are just visual.
Here's the link with information about the required inpsection that each CPO'ed car has to go through:
http://www.bmwusa.com/standard/conte...ification.aspx
The true value of a CPO car is in its Extended Warranty not in the certification itself really. Like anything else in life...when you are lucky, you got a good technician inspecting your car. When you are not lucky, you got a lazy technician who couldn't care less.
Honestly, with it being in an accident and that it showed up on Carfax, I wouldn't buy that car unless it's within the $22K range. If you really want to buy the car, use that to your advantage. If you want piece of mind, get a car that is CPO'ed and retained it.
Goodluck.