The utility company I work for trialled the DPL stuff in the 90's. Apparently it was quite successful but they abandonded the project because of potential competion from BT and the various cable networks -
http://www.theregister.co.uk/1999/09...eb_pulls_plug/
About 5 years ago, we were closing down a site with a large warehouse and I was dispatched to check out some crates of old IT kit they found in storage. Low and behold it was boxes and boxes of the modems and other kit for the substations from the project. It all went for recycling.....