I stumbled across this article by accident looking for amateur radio sites, but i found it very interesting none the less. This is article talks about two plans for data distribution over power lines. One is to feed small neighborhoods with fiber and then run them over the power line for the "last mile". This one looks to be the more promising as power lines are not the cleanest environment for sending data. The other method would be the local power distribution station acting as the fiber feed for hundreds. I think that each user at the end of this if they get it working will get too little bandwidth.
http://www.nytimes.com/2003/04/10/technology/10POWE.html?ex=1051094315&ei=1&en=4bcffa8f03673af3
http://www.nytimes.com/2003/04/10/technology/10POWE.html?ex=1051094315&ei=1&en=4bcffa8f03673af3