This is a great question, as i have been wondering this too....
I think you can drive the car off, and only when you stop engine (eg by pushing the button) you would be unable to the re-start .
(This is how our E60 works, as you can take the car out once the car have been runnnig for 30 seconds and then restart car without the key)
M6 & Family 5er
M2 & M4 CP Vert arriving in June