I watched some videos for Customtronix jailbreak for uConnect. From their product, it appears that the video is composite video going from the cameras into the uConnect system. It wouldn't be impossible to modify an existing setup to use a different camera but the connector and wiring parts wouldn't be cheap and one would probably need a service manual or wiring diagram along with several hundred dollars of FCA cables to cut up in order to do it neatly or make it look good. I could rig something to breakout the connectors and inject composite video for testing but packaging it for permanent use wouldn't be so easy. I can't figure out why the camera would have 12-pins on the connector. Composite video takes 3 to 4, depending on whether signal and power grounds are shared. RGB would take 5 to 8, depending on whether grounds are shared.
There are other possibilities for why so many pins on the connector, such as an enable/disable, but I don't get to 12 in any way. Sometimes, there are multiple ground leads or power leads just to increase current capacity but the power/current requirements of a modern camera is very low. Many of my professional security cameras draw less than 7 watts, just over half an amp, at 12v including IR LEDs with 30 to 50 foot range. Still, the extra connections could still be power or ground. They could also be simple loops or even logic to make sure you're only using approved cameras.