I was involved in a trial to deliver internet over the power cable network. The plan was to install a hub at each local distribution substation, this would superimpose the comms signals onto the mains cables, and there would be a pickup on the service cable entering each house. At that stage (late 1990's) we could only supply to around 60 homes per substation (when there could have been 200-300 homes supplied their electricity from each), and the range was limited as well...typically 300m from the substation from memory. Of course, if the power network was reconfigured (eg. due to the water service digging up a cable!), then the whole dynamics changed...it proved to be unreliable, and had questionable economics. Then along came broadband over the existing phone line and killed the idea stone dead...maybe it's time to resurrect it though!