from the recent flight ops update:

EWR – The A320 flying in EWR is sharply decreasing due to the concentration of the 320 departures out of four of our hubs (ORD, DEN, IAH and SFO, which contain 80% of the hub departures). This means most of the A320 departures for in the NYC area are actually out of LGA. Our EWR base is properly staffed on this fleet, and will continue to provide the required staffing to operate those flights out of EWR and LGA.