How do I take a fire engine to ride in SimCity 4? AFAIK it is possible to take control of almost any vehicle in the game, but I can't find how.
To directly control and drive vehicles, you'll need the Rush Hour expansion pack. If you have that installed, the game will occasionally give you various optional missions to complete using those vehicles, which upon completion will net you rewards such as improved mayor rating or extra cash. There's also a free driving mode which allows you to drive around the city in a vehicle freely.
In the original Sim City 4, you can't do any of that. What you can do is dispatch fire engines and police in response to fire, caused by disasters or the lack of fire station coverage around the city, and riots or acts of crime.