In case you were wondering what ever happened to BPL, check out this piece on Ars Technica.
One of the early real-life deployments was in Manassas (Virginia), but now the city has taken over the network, with a good chance of reducing it to a Advanced Metering Infrastructure (AMI) system. Earlier this year, a Dallas network run by Current Communications (which attracted funding from Google) and DirecTV, was sold to the city's utility.
It looks like BPL has no chance between the entrenched DSL/cable networks, and the inevitable rise of FTTH. (But then of course there is UETS ...)