I have had two cars produced at BMW's Dingolfing assembly plant(a third is on the production line now) and here is the time-line that both cars have followed.
Once the car hits 155-Production completed, it then hops a train up to Bremerhaven where it is loaded on a Wallenius-Wilhelmsen Lines Vessel bound for the port and VPC closest to your dealer. The train ride and ship loading has usually occured within 7-10 days of the cars' completion. The trip across the Atlantic to New York is generally 14 days, Charleston, SC is 16 days, Glaveston, TX is 21 days and 28 days to Port Hueneme on the west coast. I live in Florida and my cars enter through the port of Charleston, SC., where they are then loaded on another train and shipped to the VPC at the BMW plant in Spartanburg (other VPC's are located at the port of entry). My cars took about a day once unloaded from the ship to get to the VPC. Most Other USA BMW entry points don't have this extra step. Once at the VPC my cars have taken as little as 3 days to clear and as much as 8 days. Once they clear VPC and are released to the carrier, my BMW's have all arrived here in Florida the next day. So the average time in my situation has put my new BMW from 155 to my driveway in about 31-37 days. One major factor is how quickly your car can get on a ship across the pond! Once your car is on the ship ask for dealer for the ship name, which is on their DCS computer and check the schedule for that vessel at www.wlna.com.
Hope this helps. I'll be going through this exact scenario with my 2001 M5 in about a week! I already have the list of potential ships. God, I need to get a life....
'00 M5 (for sale...cheap)
'01 M5 (on the way.......)