I enhanced the original pic taken from the rear of the car in order to lighten up the shadows under the car. You can clearly see the additional finning for heat dissipation on the M diff. Additionally, look closely at the rear camber arms. You will note that they appear to be cast aluminum arms like the M3 ones, not stamped steel like the 135i/335i ones.
Here's a comparison of the standard camber link (LEFT side) and the M3 camber link (RIGHT SIDE) (pic courtesy of Harold from HPA):
I would not be surprised if BMW dug into the E92 M3 parts bin a lot for the M1. It would be an economical choice, and cost will be a MAJOR consideration for this car, as it has the potential to approach $50k.