Originally Posted by travelsmooth

Here's some brief information I can report back in case helpful to anyone. Not sure about the frequency of the TTB but they waited about 10-15 minutes for the bus. The wheelchair person that got my mom from the incoming AA flight indicated that connecting passengers can be brought up to the bus in T3 by wheelchair, but there would be no wheelchair assistance available on the T5 side upon disembarking the bus. If wheelchair assistance was needed from point to point, it would be necessary to exit out of security and make a landside connection from T3 to T5. My mom managed to walk up the steep and narrow ramp described by others upon disembarking the TTB at T5, and upon entering into T5, there luckily just happened to be an electric cart there on which she was able to get a ride to the BA lounge.