I've got a 30d with HSA (Hill Start Assist) but that operates independantly of the Auto Release of the Handbrake.
HSA automatically applies the brakes when you come to a stop (to stop rolling back or forward)
But the X3 also auto releases the handbrake when you drive off.
i.e. Stop the car using normal brakes, apply handbrake button, when I press the accelerator again the handbrake releases without touching it.