I suppose someone might use a 2 way switch (SPDT) light switch to transfer an individual load (like a fridge) from POCO supplied power via the usual circuit breaker panel to power supplied by a local generator via some form of over current protection. The switch's center contact is the load, one end the POCO and other end the generator. Probably not code, as such switches are not specifically designed or listed for such service (and might fail POCO shorted to genrator). And thus not trustworthy enough to protect linesmen.