A back up generator is a great idea BUT!!! make sure it is connected properly, if not it may kill the electrictian sent to repair the line that went down. MAKE YOU DISCONNECT THE CIRUIT FROM THE MAIN LINE BEFORE TURNING A GENERTOR ON. Someone sent to repair a downed line will likely not treat it as a live ciruit......
Anyway.... I agree your probaly good for at least a full day, the water lines in your house (assuming no other source of heat) would burst long before the burried OWB lines.
While this is good advice, I disagree with the idea that the guys making repairs to distribution level lines are "not treating it as a live circuit". they won't be linemen or utility clearance workers for long. Difficult to do this kinda work from a wheelchair or a pine box.