I Don't Think You've Thought Your Cunning Plan All The Way Through
I don't think the law is really for the evacuating citizenry at all. If the power goes out forcing the gas pumps on does no good to the station owner if there's no way to pay for the gas. No electricity in the state, people are fleeing disaster and you expect their credit cards to clear? The gas stations will have to go to cash only but who carries $100 to fill the Escalade?
I can't believe the entire legislature forgot to think about that when passing this law. So I have to draw one of two conclusions about the government that passes such a law. They either don't care about passing half hearted and poorly reasoned laws that burden their commonwealth. This would be the lesser of two evils despite the almost malevolence and malice against their constituents. The other conclusion would be that the generators aren't there for the refugees at all but are there to ensure that the occupying army of state and federal and Blackwater jack booted thugs have access to fuel during a crisis.