I flew on BA from ZRH to LHR (today) arriving in T5 (satellite area). I deplaned at 2:15 pm. Following the "connection" signs there was an agent (AA?) posted at one spot, she asked "are you flying to New York?", I replied yes, in bc, she directed me to a T3 bus stop, within 2 minutes a bus arrived, 9 minutes later I was in T3, via Fast Track I cleared security and was in T3 Flagship lounge by 2:45 pm.
The T5 to T3 bus had 6 pax (usually packed on T3 to T5). If I were only in Y shouldn't I still have access to the bus?
After clearing security I noted Delta had a special security area with lots of agents, AA has no presence in that area
[A year or two ago I connected T5 to T5, I had to take a train (within T5) and with huge amounts of walking, it took over 90 minutes to make my collection.]