Sterling Securities LLC Newark, NJ

I have been looking all over for the radio frequencies used by Sterling Securities. Their home base is in Newark, NJ. However, they are the security guards for the Shop Rite in Elizabeth, NJ and probably for several other shopping centers in northern NJ. I know they use hand held radios to communicate. I am not sure if they use a repeater system under a different license name or just simplex. I also noticed their vehicles have a very short, black rubber antenna on top. I am very surprised they aren't listed in RR or in the FCC database. They must be licensed under a different name I'm guessing. Any help would be appreciated.