Good question, from the looks on realoem it seems that there is no separate bearing.
But from the looks of the hub I would say that it is possible. I had to replace a front bearing on one of my other (non-bmw) vehicles and the dealership changed the complete hub. I later took the 'scrap' hub and swopped out the bearing. Now I have a spare unit.
So I would say it is possible, you might need to strip everything to get the exact bearing size though.