Good luck in this case. This is yet another story of a Dealership acting badly.
Also, in regards to BMW NA (not saying it is wrong or right), but they are a franchise. They usually don't care what dealerships do since all they do is allow the license for them to sell and service their cars. I haven't really seen, or heard rather, where BMW NA stepped in to help a owner out. Just wanted to point that out to keep that in perspective.
This reminds me of the case were Autobahn Ft Worth in Texas wrecked a M5 owners car on a joy ride. Dealer and BMW NA didn't help. Dealer tried to cover it up, lied, then ignored the owner. The owner took the dealer to court and won. At least that one had a happy ending. It took almost a year to resolve though, but the owner stuck it out and proved to the Dealer that he had the will and resolve, and wasn't going to be treated like the "little guy".
You can read the lengthy story here:
Basically, since posting it on the internet, like yours, it went viral. I'm sure Autobahn BMW has lost sales and customers. When you do a search for them on Google, the story is right there next to the dealership's link on google. The M5board forum community also chipped in in making this story publicized.
Needless to say, the M5 owner has a bad taste in his mouth and BMW has lost a customer.
Your story is like deja vu all over again.
A shame really. All this could have simply been rectified by the dealer fixing the issue on the spot. I'll never understand why Dealers chose to fight the simplest of things with their skewed version of "principle" when simply helping a customer would earn then dividends and loyalty in the long run.
I know you've stated all you want is an answer, but you're not going to get one unless you get a lawyer. As far as their concerned, they don't have to answer to anybody legally, unless they are forced too. They will keep ignoring you.