This was a neat read in F-Secure's weblog:

Monday, May 9, 2005
In-depth investigation of the "Cabir-in-Cars" myth
http://www.f-secure.com/weblog/

However a mobile worm infecting a car is a thought that one cannot let go easily, and even as we knew that the car cannot be infected, this was something
that just had to be tested for real.  So we got a Toyota Prius to test out the myth. Credit has to be given to Toyota for trusting their systems enough to
actually lend the car for us for such testing. According to Toyota, this Prius model had identical in-car Bluetooth systems with the Lexus models, so it
was suitable for our tests.