There are actually a couple of ways to make this happen. RF could be broadcast to remotely operate specific units or wide area units via wifi or cellular. Another way is to actually use the power lines to convey a complex electrical signal that communicates with smart meters. The ability to remotely control every house is yet another example of a two edged sword. It allows the reduction in menial work on collecting usage data, but it can also be used to tyrannically manipulate who gets power and who does not.