Couple of things to note:
Tires wear the fastest at the beginning of life. If you had a graph of tread depth vs mileage, it would look more like exponential decay than a linear graph.
With regard to alignment, it is possible to get accelerated but relatively even treadwear from a car with aggressive toe settings. Camber is the more common issue for BMW, and that would cause wear at the edge, usually negative camber and inside edge wear.