I know the guy flying the drone over New Years. They were based on a barge right among the other fireworks barges in the harbour and yes it was pure luck that they didn't get hit by any of the fireworks but as someone has already said it was a cool shot and they decided it was definitely worth it.
They were in a cordoned off area over water so if it had been hit there was little to no risk of injury if it fell and for the cost of the whole NYE spectacle in Sydney the cost of a drone is nothing.