A few years ago, the idea of running high speed data networks over electrical supply lines was floated, tested, and scrapped. It didn’t work, as I recall.
However, Scottish & Southern Energy have tried again, and this time the technology has been tested and is working, according to this story.
A 2 Mbit symmetrical connection over the pre-existing power supply network is pretty good. It might even provide a good way to cut those overcharging monopolising phone companies out of the loop. Wouldn’t that be nice!