Are government-owned vehicles required to have ID cards?

No. However, if you are planning on out-of-state trips, you should have an ID card. The requirements vary by state. Within the state of Tennessee, per Financial Responsibility Chapter No. 292 Public Acts, 2001, vehicles are not required to have them. They meet the Financial Requirement per section (a) (3) of the act: “The motor vehicle being operated at the time of the violation was owned by a carrier subject to the jurisdiction of the department of safety or the interstate commerce commission, or was owned by the United States, this state or any political subdivision thereof, and that such motor vehicle was being operated with the owner’s consent."