Bigger thread here http://www.flyertalk.com/forum/ameri...er-thread.html but I think the view is that if your flight is not from TBIT then you're "encouraged" to use the lounges in T4

I'm going to try this next week as I'm transiting T4 but have a few hours to kill and my nephew is going through TBIT so I want to guest him into the TBIT lounge before heading back to T4 - will report back on my success (I'm a BA Gold / OW Emerald if that makes a difference)

Hope it works though as IMO the F lounge in TBIT is one of the best in North America