I have the same problem with my 06 750Li. 80,000 mi. Smoking and burns a quart of oil @ about 2,000 miles. Dealer says valve seals leaking oil into cylinders. Repair will cost $6,500. I was thinking about having my local auto mechanic do an engine oil flush to clean out oil sludge build up. Not sure if that is a safe procedure.
I had an engine oil flush done and it did not work. It still smokes and burns 1 quart/1,000 mi. I found a service station that works on BMW's. He quoted me $3,200 or less for "valve stem seal and gaskets replacement." Needs vehicle for 5 days. I will keep you posted.