They probably would if they could. That gives me some bad ideas - you could vary the line frequency to play the McDonald's 'I'm Lovin It' jingle, etc.- good thing I'm not involved with either ads or power delivery.
You could make this work! I saw a project once that used some open uk power grid information to triangulate videos by listening to the background hum. Genius but also a real "oh god what have we done" moment for me.
