Just received an e-mail from BA that this Quintessentially service thing is now available to FIRST and Club passengers from JFK.
Originally Posted by BA
This service, which can satisfy last-minute requests for everything from dinner reservations to theatre tickets, is available to passengers online and in the JFK Terraces Lounge courtesy of British Airways. For more information, please call 1-888-269-4248.
Seems a bit strange to want to arrange theatre tickets when departing New York, but I suppose one could plan ahead (I just get backstage passes

).
Had a stroll through their website and they seem to focus more on parties they throw rather than the products they promise; all very glamorous and exclusive, but perhaps no much substance? And all reads very vaguely IMHO. Comments above seem to confirm...