I assume you are listening on a digital scanner and are monitoring the 800mhz system. That is a statewide system, and it is a Motorola SmartZone system. The way SmartZone works is that a talkgroup will be carried on a site only if a radio is affiliated to that site on that talkgroup.
The state is broken up into zones, 3 of which reflect the 3 counties, and for the most part, all the sites in a county/zone simulcast anything that any other site in the zone transmits.. The Kent County talkgroups frequently show up on the NCC sites, and they are being transmitted locally from the NCC sites. What that says is that someone has a radio on the system which is currently affiliated to an NCC site and that is monitoring one of the Kent County talkgroups, hence pulling the Kent talkgroup they're listening to up on the NCC zone. There is an NCC site right on the county line between Kent and NCC, so you'll frequently see Kent County radios affiliated to at least one NCC site.
This dynamic way in which talkgroups are made active on a site helps to preserve available frequencies at the repeater sites. There are a limited number of available frequencies in the pool that can be assigned to a talkgroup when someone keys a radio, so by only carrying talkgroups that have radios affiliated to them on a given site or zone, more frequencies can be kept available.
The NCC zone does have quite a good coverage area. I know I can receive it almost anywhere in the Southeastern part of NJ. Some of the UHF patches also have similar reach.
-Ryan