I don't have any 9-speed, so I don't know for sure, so I'm using logic & may be wrong:

1. I wouldn't think they'd have to be used with a specific Campy FD. I'm currently using Record Ergo 2x8 with an old C-Record FD. I imagine one could use pretty much any FD with Campy Ergo.

2. I'm not positive, but I think my brother is running Sachs Ergo 9 with a Campy RD. Or maybe it's the other way around. In any event, I think that if one were to want to mate a non-Campy RD with Campy Ergo, one would need a Shift Mate thingy, or possibly a Sachs RD.

3. you could probably get away with running a Shimano cassette if you used Campy spacers, if they'll fit. When I ran a Shimano cassette on my old SunTour XC Pro, I used SunTour spacers and it shifted beautifully. I would not have been able to do it the other way (Shimano spacers on a SunTour cassette), as the SunTour freehub body was of a larger diameter than the Shimano freehub body.