As for crewing, CityFlyer aren't getting near it
Very true mate. There has been a number of posts regarding this new routes that have said BACF crew will be operating the flight. When BA announced the route it was announced as a BA mainline service not BA operated by BACF to JFK.
BACF is a subsidary and as such is seperate from BA mainline.
The flight will be operated using A320 family rated flight crew and the purser and two main crew will come from the LGW fleet who already operate the A319 ex LGW.
The closest BACF will get to it is when they park one of their shinny new Ejet on the stand next to the A318.