The camera chip that Tesla is using in the Model S is the OmniVision OV10630. The
data sheet reveils that the sensor supports a digital video parallel port and 8- or 10-bit YUV and 10- to 18-bit HDR RAW output formats, but how Tesla has implemented the chip and what connector they are using I don't know.
If we know more, it may be doable to "intercept" the cable and add a switch and video port to allow an alternate video source.