Since I did not find actual FCC licenses (ULS system) under their actual business name, there is a good chance the are using a large communications provider or local (mom & pop) radio shop to either lease time/space (on repeater(s) or Talk-Group(s)). They would then be under the providers FCC Call sign. Two possiblities are listed below.
Atlantic Telecommunications
https://www.radioreference.com/apps/db/?sid=8464
OneVoice Network
https://www.radioreference.com/apps/db/?sid=7363
If its a smaller Mom & Pop radio shop it may be difficult to find unless one want's to research FCC licenses (ULS)for them - a long and ardous process. Finding the shop's name and if they cover the area.
They also can be using regular Cell phones or a cellular LTE PTT network, then unfortunately it's not monitorable by any scanner.
To the group: Any help on this is appreciated