fwiw, michelin does offer a runflat ps2. It's called the ps2 zp and a number of 335 owners report having the tires.
the tread design is identical to the ps2s.
with that said, I haven't looked close enough at oem m3 tires to see if they are infact the zp version. A number of dealers are instructing owners that the tires are runflats so hopefully they have their ducks in a row.