My Czech-built 2015 GD doesn't have CAN bus, or at least not to the rear light clusters. If you look at the wiring to a light cluster, there would normally be one wire per light plus another for the ground, whereas CAN would have 4 wires, 2 thickish ones for power and ground, and 2 smaller ones for the data bus. You don't have to have CAN to report bulb failure, the current to the bulb may be measured at a central lighting control unit so it will know if a bulb has blown. I haven't noticed bulb alerts on my car but in the 5 years I've owned it I can't recall having any failed bulbs.