My understanding was that Canon purchased ED glass from Nikon for manufacturing lenses, I have seen it referenced more than once, but I don't have the article either. Maybe it is a myth, maybe not.

I am not sure what the big deal is if it is true, since we are talking about glass here, not actual camera lenses. It is very common in telescopes as well, with Nikon producing some of their own scopes, and other manufacturers purchasing Nikon glass for their products. Nikon just happen to have the capability to make some very good glass for optics. It is used in eyewear, binoculars, etc. It is a different line of business than their camera business.

As for GM and Ford, well that is pretty common too. I have driven Ford Class 8 trucks with Detroit Diesel power (before Penske owned DD). GM Allison transmissions are everywhere. Components are commonly sold between manufacturers, although I think that they would likely prefer not to talk about it too much. Hertz will gladly rent you a GM vehicle, or just about any other brand, despite their ownership (OK, that one is changing).

Back to BMWs, even the X5 3.0 has a GM automatic.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue