There are only five frequencies in the FCC database assigned to Shelby for the trunked system.
Possibly you were counting the number of records, which is six ... five sites, and the license for the mobile / input frequencies.
They would also, by default, have access to conventional use of the five ITAC frequencies. If they wanted to use them with a repeater, the frequency would have to be licensed and coordinated.
Occasionally, I will run across an agency that has licensed an ITAC or tac conventional channel as trunked. A hobbyist should become familiar with these frequencies, so they don't program them as part of the trunked system ... and end up not hearing anything on the frequency.
Jeff Multer