Found the latest version of that PDF above and other docs. Sounds like mostly a software upgrade to the sites and radios, and most radios will work on the old and new system at the same time. Once all radios in an area are updated, the towers will cut over. Sioux Falls and Rapid City will be more complicated. Network updates are required and proceeding. Current towers will be used, and still on VHF since no radio replacement is required. Suspecting frequencies all stay the same, and that talkgroups would too. Lastly, it will likely be P25 Phase 1 since Phase 2 would require more changes and higher cost. Looks like encryption is available as it is on the current system.