You could try asking Lionel direct on the TalkToUS@lionel.com contact. I recently got, and very quickly, an answer in response to a Vol.2 catalog query (whether the powered F3 B unit has a smoke unit, which the catalog did not mention although smoke is standard). A while back I also asked them about the 21" UP excursion diner and got confirmation which prototype it will be based on; the catalog picture showed one while the text referred to a different diner.
All the 21" StationSounds Diners released to date have had railroad-specific sounds. They are actually some of the best products Lionel has released lately in terms of sound effects. So I'd imagine the AFT will have something distinctive but as you say, the catalog description is very general.