How far do I or can I transmit into the grid? How far do load changes from my house transfer into the grid? Surely my neighbors could detect 1us spikes not big enough to pop mains at say 800hz?
I expect the incidental signals your usage generates are going to be hard to detect past your power meter and almost certainly un-resolvable past the distribution step down transformer.
Me and some friends tested them and tried transmitting to a neighbours house (connected to the same electrical post) and had no success at all. There was just too much noise, coming from other houses. However with digital technology I'm sure you can get a much better range.