+1
The maximum time for a smooth switchover like that should be 24-48 hrs. It can be done from their office.
I discussed this on Friday with a friend who's a plumber. He told me that ever since some 2nd avenue explosion, the city has become a lot stricter with inspections, but they didn't increase their workforce for doing inspections.
If gas was shut off to a location for six months, you cannot have it turned on without doing a pressure inspection. So if it's an immediate switch of the account from one tenant to another, that should be smooth, the problem starts when there's a lengthy period with no service.
So in my friend's words, if they were bribing to get an inspection ahead of time, that would be somewhat OK under the circumstances, but hooking up gas after a period with no service, is a major safety issue, and bribing to get that done could be putting people's lives in danger.