CAN-BUS is becoming the bus of choice. However many makes and models still used mixed protocols for different components such as ABS, ECU, Airbags, Body, Power Steering etc.
I don't think FIAT are using any of the newer bus topologies (which seem to be mainly developed by the big german manufacturers, and hopefully they'll forget about using them ). FIAT have been using CAN bus since 2000/2001.. other than that, they are using much the same electronic systems / layouts as any other manufacturer e.g. GM.