Fire Dept vehicle designators

[gldavis]

I'm currently updating my list of RID designators for Weber Co/Ogden Fire/EMS units, and I have some questions that someone here might be able to answer.
Difference between Ambulance-XX, Medic-XX, or Medic Ambulance-XX? Or are they all interchangeable?
Difference between Engine-XX, Transport-XX, Engine Transport-XX? Or again, are they interchangeable?

 

[Spadinator]

Ambulance xx is an ambulance crew the number designation is the area they serve. Medic usually is a rescue truck that does not transport. Some agencies have both combined into one unit ambulance/ medic.