Actually I got a note today from my dealer saying that production started this week.
But bear in mind this is really a car that my dealer ordered for their own stock and then changed the specification to meet my particular needs. The US car market is primarily one where customers buy "off-the-shelf" so they need to have a lot of stock. Today my dealer has 104 new 3-series cars in stock and this is a quiet time - how many dealers in Europe have anything like that quantity?
In the UK even when I bought a new BMW that was in stock (rare as they had so few) I was told to come back in a few days whilst it was "prepared'. In the US you expect to buy it and drive it home half an hour later.