BPL is a neat concept for very rural areas, but was expensive (iirc a broadband regenerator unit is needed for a certain length of line (Ex: every 1 mile) and is not cheap. Also, the interference for things like radio communications was never really accepted.
i dabbled in it early on for LAN usage. This or a varient of this tech is apparently how the electric utility predicts power usage and upgraded line requirements, in my area.
they send a report along with your bill and it contains a graph of daily usage, and you can see houly usage and current spikings online. Im sure they know more than they are telling, and probably searched for certain devices before legalization of a certain brand of tobacco.