Anecdotes of appaling BMW reliability are so prevalent in the online enthusiast car communities, and shade tree mechanic workarounds are so well doumented, that I would question any statistics measuring otherwise. Lies, damned lies, and statistics...
The opinion of luxury equaling low repair rate is simply not anything I've ever heard before. Are you staying that it is? I added an anecdote with my personal experience, but an anecdote neither proves a point nor refutes it.