We don;t have any examples for networked cars right now but it wouldn’t be that difficult to build them. In the end GoPiGo’s are Linux boxes on wheels. A simple socket server could be used to communicate between them or you can use something else too. One you have got communications working between the cars, the next thing would be to send messages between them, parse the messages and run appropriate commands. We have this example which shows how to use sockets to control the GoPiGo https://github.com/DexterInd/GoPiGo/tree/master/Software/Client_Server. You can build up on this so that multiple GoPiGo’s can communicate with each other.
We would be more than happy to help you develop this project.