That happened to me in Sydney once. We had about 20 minutes before curfew with permission after that denied. So we called ops who said forget the passengers just get back to home base we can’t cancel the flight tomorrow morning back at home base as no seats for days to re accomodate.
The only issue with T2 Sydney is the windows/passenger lounge sit right in front of the cockpit. So when we pushed back was a bit of jumping up and down in front of us.
Rule number 1 is never take a last flight from Mascot!