According to AutoBild (picked up by Reuters) and MINI2:
Mercedes to Share MINI Platform?
BMW may be considering platform sharing with Mercedes, Honda or PSA.
Seems a bit vague and 2+2 = 7 at the moment, but what would you think if the MINI platform was shared with another car, any other car, BMW or not?
Would it cheapen the brand, make it less unique?
Or is business business, and as long as there's no negative impact on the MINI chassis and handling, then there's absolutely no reason not to do this?