Usually the airport authority will unlock them prior to the arrival of the outside safety services.
No they won't. terrain safe is entirely correct. Crash gates are to allow the airport RFFS to get out.
Outside safety services will report to the designated rendezvous point first and be deployed to the accident / incident inside the fence as required. There will only be one or two RVPs dependent on the airport layout and the message alerting outside services will inform them which one to go to. The RVPs could be at a crash gate in which case they would be manned pretty quickly, but most RVPs are at points that are already manned, quite often the fire station
However, there will be many more crash gates around the airfield.