There are many different types of Federal Excess Property Programs where LE agencies, fire departments, municipalities, etc. can acquire vehicles and other equipment for their use. They vary from state to state, but in my experience, there are two basic ways that property can be acquired.
Sometimes they acquire property on loan from the government. It must be returned when the user no longer has a need for it. This is where many of the vehicles that are sold through GSA auctions come from.
It is possible, especially if acquired in the last several years, that the Sheriff's Office actually purchased and owns the truck in question. Generally when an eligible organization purchases excess property at a discounted price, they have a certain amount of time (a year, for example) to make any necessary repairs or modifications to put the item (truck, in this case) in service. Once in service, it must remain in service for a certain time (two years, for example) before they can dispose of it.
Once again, there are many different property programs where they can acquire vehicles and other equipment. As long as they actually purchased and own the vehicle, and have had it in service for the appropriate amount of time (if required under the program they acquired it from), you should be good to go.
