I wonder if they thought that since they were responding to an emergency, and they were given clearance to cross by ATC, that that would override normal procedures. Kind of like how emergency vehicles cross a red light all the time when responding to an emergency.
It would be interesting to know whether that rule was onerous enough in practice that they had little choice but to break it in order to do their jobs effectively. They were responding to an emergency, seconds count, and they believed they had clearance from the controller.
