I really don't see how this would be either cost effective or even workable. Coaxial cable works well because it has an outer shielding on the cable that keeps out external interference, but power lines lack that shielding. From the standpoint of offering broadband, it's not what gets out of your lines and bothers the amateur radio guys, it's what gets into your lines and corrupts your signal. Also in order to run an RF signal you need amplifiers spaced at regular intervals, the higher the frequency the more amplifiers, and who in the world is going to want to do the maintenance work on amps that are hooked up to primary power lines? They're not like transformers that you can just leave there for decades at a time.
16kv gloves; might present a problem when trying to use a screwdriver...