I saw this car whilst shopping for my 4-door. I actually went to look at a white M5, but was told the dealer had just found out it had had it's warranty voided by BMW (the white M5, not this one). So, when I passed on it, they showed me this.
The guy said it was "his bosses car" (that he was going to keep it for himself). It was parked around the side of the dealership, was dusty and looked GHETTO. It looks ok in this video though.
Luxor Auto in Scottsdale (south side of the city, on Scottsdale Road). They've got some stunning auto's, but have a penchant for putting some awful rims (imho) on them.