Umm, this actually is an official BMW design, as in it was produced by a designer (yes, working under Bangle) doing concept sketches for the Z3 replacement, the Z4.
If you look at this car, you can see where the ideas for the Z4 have come from during this concept stage. In particular, the balance of the car's styling and its proportions (especially front-to-rear balance), more agressive headlights, and Z strike lines running along the front guard to the door, sweeping down to the bottom of the wheel well, then along the base of the door.
I saw the 2D renderings of this EXACT design in a magazine called Deutschland in an article on German car design. The renderings were supplied by BMW, and the signature on the pics was neither Bangle's nor van Hooydonk's (sic?) (van Hooydonk is the guy who designed the 7).
THIS CONCEPT RENDERING COMES FROM BMW.