Union > Woodbury and vice versa occurs on the digital STARCOM system that covers the entire tri-state area. Through that STARCOM system, they can tie different systems together - whether it be Iowa's 800 MHz or SD's digitial or VHF systems, but only when interagency interoperability is needed. 99% of the time, if UCSO or SDHP needs to talk to someone in Sioux City (Woodbury), they do it through Union County dispatch.
Here is the weird thing - both agencies in North Sioux City (PD and FD) are dispatched/paged by Woodbury County, IA rather than Union County, SD. So, that being said NSCPD and NSCFD are the only two agencies in the area that I know of that carry in their vehicles the capability to talk over all systems used in the area (IA digital, SD digital, UHF, and VHF) without dispatch interoperability intervention on the STARCOM system. NSCFD now even has a few handheld radios that cover the entire spectrum as well...
Hope that makes sense.