RS starts your vehicle like a human, it eletronically presses on the brake and then press on the keyport as if a key was in there. Once the vehicle is running, the key is not needed in the port if a successful takeover was done. Similar to the models that have both the keyport and the push to start button. You will definitely want to put the key in though to atleast be able to shut off the car after your drive.
As mentionned by Derek, takeover is handle by unlock. As long as the module see an unlock signal, vehicle takeover will be available. Otherwise, if someone breaks in, the RS will shut down on door open or brake press.