I've made it over to lounges in TBIT when I had a long connections on AA (T4). No problem with access. I wouldn't bother again: it's quite a hike.

If you are curious, and you have time on your hands, you should first check that T2 and TBIT are connected airside. Sadly, I think the tunnels and walkways connect TBIT only through T4 to T7. You probably wouldn't want to throw two sets of security into the equation