A plane that has no passengers on it? Requires the full turn out of the entire fire fighting operation? How about using some common sense and despatch a couple of units to fight the fire leaving a complement that is sufficient for normal operation then IF the fire gets out of control summon the rest for assistance. As I said its a knee jerk reaction typical of the world today.
Fire brigades have always worked on a worse case scenario basis. A minor fire in a waste paper basket at an oil refinery might get something like a dozen appliances on the way immediately, another dozen following within ten minutes etc. I would think they do similar with an aircraft fire and treat it as if it was full of passengers and full fuelled up rather than wait whilst they make a few telephone calls first to check. With all fires they like to be absolutely sure they are completely out before leaving the scene.