Offensive frequencies are on the order of the electrical length of the cabling. Typically 30MHz+, but long cables can be problematic much lower. For mains, telecom and so on, they use conducted emissions more as a convenience I assume (otherwise, you'd need to do a more sensitive, open-air test, with very long cables and antennas).
Yes, any induced RF between grounds going in and out of a module, is a problem. Or more generally, the common mode, taking the average over all signals in the cable, weighted appropriately of course (since signals inside a bundle, or inside a shield, will count less).
Tim