A number of smart meters communicate over the mains wires, especially when they're in very sparse areas. There was even a thought for a bit to offer internet services over the power distribution cables, but I don't think they ever really got effective data rates high enough to be competitive.
Yes, that seems to be what mine is doing as my ecobee thermostat is able to read info about peak usage times from the mains. I didn't know about the latter part though, I never imagined electric companies were making a play for the internet (though it seems like an obvious thought in retrospect).
A lot of electric companies in the US are also ISPs. They already have most of the equipment to run fiber, and many also do wireless links between substations.
And its "last mile" friend of using the in-wall cable as Ethernet drops, too, e.g. https://www.tp-link.com/us/powerline/ (but I don't think it holds a candle to actually pulling cat 5 or 6, for clarity)
In the early 2000’s there were efforts to provide broadband over power lines (BPL). I think one of the biggest obstacles was the radio frequency interference it generated.
Re-reading some of the history of it that does sound like RF interference was more of a concern than data rates. Some places even attempted roll-outs but were stymied by regulators wanting more studies about potential impacts.
If it's low enough bitrate, wouldn't you be able to read that by putting an antenna or loop of wire near the mains? I assume they use a documented standard.
