Yeah I imagine for lines outside the home, or in public places, it would be best to assume that the channel is untrustworthy and the data is public. Essential comms would need to have redundancy of course. But for an oven reporting its at temp, or a thermostat reporting its room's temperature to a central HVAC controller, I think it would be nicer than running everything over wifi.

You could even have a signal smoother at the main so nothing inside the house can get out. The way I'm imagining it, all the household power would come from the home battery, which would be fed by a combination of solar panels and grid power. If the battery's full and the sun is shining, power feeds back into the main. If the battery's low, power is drawn from the panels, and if that doesn't meet demand, power is drawn from the grid. But the whole house is buffered (electrically and informationally) by the battery.