That's not inefficiency. That's precautionary, and SOP in most first-responder units. Rarely do first-responders know the extent of what the situation on the scene is going to be before they get there. Diesel and miles on the truck are cheap, and peoples' time is a sunk cost.
Don't take my word for it though, the Mayor of Provo answered the question much better:
"I’m often asked why we send a fire truck on every medical call. Does it really require an ambulance and a fire truck for many of the minor injuries? It seems a waste to drive a very fuel-inefficient fire engine to something where the additional personnel are not needed.
While there are some calls for emergency medical assistance that can easily be handled with just the two personnel on the ambulance, there are many that require additional help. Nearly every EMS system sends a unit to “back” the ambulance for a number of reasons. First, nearly every life threatening emergency incident is best handled with at least two paramedics in addition to the driver. Second, there is not always enough reliable information on the patient condition to determine if additional help is needed. Valuable time may be lost if additional personnel are not dispatched until the ambulance arrives and makes an assessment. Finally, even so called “routine” medical calls often require the patient to be lifted into the back of the ambulance. Even if the patient is not obese, it is safer for the patient and for the backs of the medics to have additional help to lift.
When the fire truck is not needed on an incident, it is released to go back into service as soon as possible. The cost of the fuel to have the extra help immediately available when it is needed is a small cost when compared to the loss of precious minutes when a life is on the line."
That explains 2 of the vehicles. It still does not explain the ladder truck or the fire engine.
> Diesel and miles on the truck are cheap, and peoples' time is a sunk cost.
Is a fair point. That ladder truck exists just in case an earthquake breaks the water lines and sprinklers stop working. I still do not see my city (or many others) as shining examples of efficiency. This does not mean I want to privatize things like fire departments and police as that would has its own issues, but neither do I think cities are so efficient that we should have them handle more things.
Mine doesn't. I saw a ladder truck, a fire engine, and multiple other vehicles show up when one guy passed out and need medical care.