We own our building, so the town pays "rent" to us to store "their" fire engines. We basically "agree" to operate/staff the trucks and respond to fire calls. We also have another budget to cover operating expenses, fire gear, equipment, etc.
We don't have a fire tax, we are in the general fund.
To buy new trucks, our town has accounts that they put roughly $50,000 a year into. That can be adjusted up or down depending on how long till we estimate we need to replace a truck. When a truck comes "due" to be replaced, hopefully the money is already in the account to cover the cost of a new one. Sometimes it has to be supplemented, but usually not by too much. This is a remarkably intelligent way to buy trucks, and has been in our town budget for decades, so there is usually no problems come budget time.
We have a BIG dance every fall for our own budget to cover everything else.