Originally Posted by Kotts

I believe the answers are "No" and "Yes". I'm being tentative in part because I'm not sure I'm understanding your questions correctly.

I don't think Campy cranks will fit on a Shimano spindle, because the splined types are different splines, and the square taper types are a different taper. However, I'm no expert on Campy.

A Campy REAR derailleur would attach to the bike by the rear deraileur mount, at the rear dropout. This should be no problem. The only part of a bike frame that is "English threaded" (vs Italian threaded) would be the bottom bracket, and I can't imagine how that would affect the rear derailleur.