Original : http://www.techwatch.co.uk/2011/01/02/liverpool-to-trial-200mbs-powerline-broadband/
According to Brian Turner over at tech watch Liverpool council is go trial broadband over electricity cables and at 200mb's that's fast.
From what I can make out it's not exactly like the local Ethernet over your houses electricity network. They talk about having to install hardware in the 1000 new builds that are going to be part of the trial and there might be some issue with interference with radio signals. The broadband would be at a different frequency than the electricity.
Originally read from Tech Watch