Not a BMW development driver (full face helmet).
A pretty normal external antenna for 2-way radio (advanced telemetry...??!!)
BMW badges uncovered
Testing with other manufacturers around (or public)
Tuner testing aero add-ons (they look like prototypes to me, as no-one would have such tacky struts to hold the rear wing in place).
Or.......BMW testing market reaction to the idea of a GT4-alike M3 (without actually putting a real car out in public) and all of the above is a bluff.