I don't think this is true. In theory you could embed the cellular modem into the mainboard, or even into the processor, but I would bet for ease of service that the modem will always be on a separate board somewhere that can be cut off.
They would never make the car reliant on cellular service or it would just stop working whenever you didn't have a signal - or the modem died.
They would never make the car reliant on cellular service or it would just stop working whenever you didn't have a signal - or the modem died.