If by all means you have to get rid of that firetruck, as if it would end the world if you didn't delete it, you should make sure to leave the firefighter profession to then delete it. Otherwise, simply dragging it into a Big Parking Space (it's the only parking space that fits it) and then using something like Detonate (Inventing interaction) or testingcheatsenabled true to shift+click and Object>Delete it.