If I'm not mistaken, that is in fact a font but it is exclusive to a particular fire apparatus manufacturer and it has been requested here on many occasions. Some years ago I had a conversation with one of the staff of the sign shop at one of the manufacturing facilities regarding either that font or a similar one and I was told that they digitized it based on a typeface one of the old timers used when hand gilding. I cannot recall which manufacturer it was.
Closest I have are Newtext & Modesto...
It's definitely a font, as it's on all their other trucks in the pics, it would help in identifying it greatly if he had a pic of the text not arched.
If the manufacturer would have lettered it I could tell you, but since the local dealer subbed it out I can't get it.
Here are the local dealers: http://www.spartanerv.com/dealers.aspx?state=California
He could possibly call and see which one sells to that dept, then see who did the lettering on their new truck; then ask them what font was used.
More than likely it is a digitized personal font from the original gilders lettering types. Having done quite a few firetrucks for a dealer down south here and communucating with quite a few "Firetruck gold men" over the years, I can assure you it was common practice as soon as dealers started wanting and calling for signgold many gilders digitized their own trademark fonts to keep their past clients happy and getting the same styles they had been paying for in the past,...I assure you when a client spends anywhere from a quarter to over a half million dollars for a vehicle they don't like seeing sudden differences in their identification due to a supplier not having the same font they have bought and paid for over a couple of decades and have come to expect,...I have been told many times the reason the fire dept came back to the dealer we served was among many other factors the consistency in the way we lettered their trucks and how well it held up,.....