Hmmm,

Ever try using a cable that runs directly over the top of a light ballast? How about one that is near a welder? I've even seen excessive noise on cables that paralelled power lines going to 2 hp motors that had brushes going bad.

IMHO I just don't believe it based on field experience. Relocating the CAT5 in the above situations has worked for me many times.

I don't think the problem in the above cases were actually caused by the power itself, just that the strong magnetic fields involved DO have an effect.