Never tried it, although have run Hayes Stroker Ryde with Avid CS2 and 3, also Shinamno M596 with Avid XX, no problems. The rotors seem fairly compatible in width, just be careful with the diameter, 180 vs 185 and 200 vs 203. I think I would usually try to match the rotor and caliper in the ideal world.
should be fine. The best reason is, that when you get tires of screwing around with the Hayes 9s, you can just throw Avid bb7 calipers on instead! I have been running bb7s with Hayes rotors (from my Hayes 9s days) for years. Works great.