Power lines do radiate electromagnetic fields of energy (EMF). I'm sure you've heard of the health concerns of people living in close proximity to these lines, especially the very high voltage lines. So see, this energy can radiate more than a few feet. I'm personally not too concerned about RF interference from these lines, but if there were a mechanical imperfection like a cracked insulator or maybe a non-linear load then this could definitely create a harmonic radiation which could cause a problem for a nearby receiver. No telling what kind of harmonics would be radiating from a problem of that sort, and I'm sure an emission of this sort could travel quite a ways. I think the frequency of power lines is like 60hz, but any problems with the line and then you may have a harmonic radiation which could easily be in the khz or mhz frequencies.

Wade