Have never had to show ID to the dragon guarding the Fast Track Queue.

Wouldn't recommend it though. If it does notice that the BP has already been scanned, who knows what security crisis would be triggered.

If you want to find out whether the scanner does keep track, why not give a second copy of one of your BPs to one of the Smirny Jnrs and see whether the machine picks it up when you next go through. At least you'll be able to explain that as a printing mix-up.