Detroit Mayor selling city used cars to save money

Here's an interesting story about Detroit Mayor Kwame Kilpatrick having to sell city owned vehicles to close a $230 million budget shortfall. What's worse the city spent $25,000 to lease (lease!) a Lincoln Navigator and no one knows who is using it. That's bright. My big question is why does the city of Detroit have to buy its vehicles? Why haven't the big three, in appreciation to the city, offered them some fleet vehicles? I'm sure there are enough Ford Focii, Chevy Impalas and Chrysler Sebrings around that aren't being put to use.