This is very interesting and many of the BMW dealers (owned by BMW) here in Germany have said that the major problem would be sales. It seems that Americans don't want diesels because they think that they are too slow and have no power. Well, after driving several BMW 3 and 5 Series TDI here on the Autobahn I can tell you we have a very bad misconception on that part.
The other reason is the grade of diesel available. Even though it is posted on Wikipedia (a great source for information
) the problem is that there are still a lot of high sulfur fuels out there that could damage the engine and BMW is waiting for that to change before moving them into country hence the projected time line.
This is information that I got from BWM Neiderhausen in Mannheim Germany. They are a fully BMW owned dealer. Why? Because I was curious.