Ok, I managed to answer my own question. If there is a button present directly below the shifter then the car has Adaptive Drive. See the 2007 X5 Owner's Manual here:
http://cache.bmwusa.com/PDF_6cc05348...7-732719793466
The button (labelled number 21 on page 14) is for 'Adaptive Drive'. According to page 86, Adaptive Drive is always on but it can be set to either Sport mode (LED in button lights up) or Normal mode. So there is a physical giveaway if a car has Adaptive Drive or not - look for the button.