Can 1-wire (One-wire) sensors be used over power lines?
The device you inquired about, the DS18B20, can not be directly connected to AC power circuits.  It requires a DC supply of 3.0 to 5.5V.  Some sort of power-line modem or interface circuit, at a minimum, would be necessary to connect a raw sensor IC such as this to an AC power line circuit.  Anything that involves communications over 110V AC power mains should not be considered a "do it yourself" kind of projet.  I would suggest sticking to the Home Plug AV devices you mentioned, or similar commercial power line communications devices.