Not knowing the exact situation generally a seizure is not a life threat. Young children have febrile seizures when they run a temperature which you treat with cold packs and keep the airway open. Scary yes, fatal, no.
In PA where I live you have to be an EMT to give a patient O2 so they may be in trouble for that also. This is not a problem with the fire department, it’s a problem with the regional EMS council. It’s called practicing medicine without a license.
One other small point, EMS as with fire, will use the nearest truck that is available, mutual assistance. We use trucks from out of county if all ours are in service. Both fire and EMS do this. This was in my opinion a huge screw up on the part of the firefighters.