No we don't use oil pan heaters, or at least the smart people don't. Its an engine block heater. I wouldn't heat a battery I would just ensure I have a cold climate battery that has 900 cold cranking amps.haha, I live in the upstate of South Carolina, you think 50 is cold? last night it got down to 19F at KGSP (airport, which I live 10 minutes away from), 50 would be like spring, lol.
Btw, concerning the cars, Heating the oil is great, but what about the battery? Cold is far far worse on the battery than it is the oil.