From what I recall, each unit has its own repeater that all of the unit-local handhelds use. For several years I lived outside of New Waverly near Phelps, and I easily could pick up Wynne, Ellis, Hunt, Byrd, and Goree, as well as Polunsky, with a Motorola Spectra that I had programmed with all of the frequencies. Reception was generally better at night for the further units like Polunsky, on a 1/4 wave whip that I mounted on top of a power pole outside of my shack, about 30' AGL but I could easily pick up the closer units day and night using a 5/8 wave mag-mount whip stuck to the side of my shack on a piece of sheet steel.
I would suggest scanning around 150-158 mhz with a scanner to see what you can find, that yielded most of the frequencies I programmed; they aren't hard to find.