Looking at the vid, the first sequence is definately real-time, the second is slow-mo, so in my humble opinion, the AF is motoring way above a safe night time confined space taxi-speed.
So, the AF PIC is at fault for taxing at a higher than normal speed in a confined ramp area, but, the Comair PIC must hold some responsibility for not calling "not on stand" or "not yet parked" to ATC. Surely in a confined area such as JFK ramps, when you know someone is going behind you (possibly knowing the AF was holding down the taxiway) you have a duty of care to other traffic and ATC, to inform them your butt is sticking out on the taxiway.
Scary event for the CM pax and crew.