Just beware that there's a "bouncer" at the bottom of the escalators leading up to TBIT security from the check-in hall, who is there to check that everyone going up has a valid BP. I've gotten pushback for showing a UA BP. You might have to be firm and say that you know how to get to T6/T7 from TBIT and that you're there to use a lounge, or if you have an old mobile BP for AA or a TBIT airline that might do the trick too.