When the terminal transfer bus is back at ORD, is it also possible to pass security at T5 (for my BA flight) and take the TTB to the AA lounge at T3? Or is it only one direction, from T3 to T5 and empty the other way around?

The BA lounge at T5 ORD is unfortunately a dungeon without windows, so was hoping to hop over to the otherside of the airport.