A few ideas:
1. Like Revamps posted, don't escorts have drivers who are paid by them to drop them off and pick them up? Who were the drivers for these girls?
2. About the phone calls made from the discovered cell phone: I wonder if the caller had some kind of accent, I mean any kind of accent i.e Bronx or any other local kind, any inflection in the voice that could tip off where the caller lived or grew up. What was said? How was it stated? All of these types of things can be important to building a profile IMO.
3. Like others have pointed out, I believe there may be other bodies located at another dump site. I wonder if another beach is the place? I absolutely think there is a connection between Atlantic City and Long Island, even though the clothes/non-clothed aspect about the bodies is strange. Where next? Cape Cod? IDK but I think there will be another location that is a beach.