The DMR experimental license is WK2XIK (Northern California GMRS Users Group / NCGUG). You can find it here:
https://apps.fcc.gov/oetcf/els/reports/CallsignSearch.cfm
We operate two GMRS DMR repeaters in the San Francisco bay area. Their purpose is to evaluate how digital might co-exist in a shared channel analog environment. So its not a technical evaluation. DMR had been around for about 8-9 years and is well established, and exceeds all the GMRS RF technical requirements, except for the emission.
This test might also apply to NXDN, dPMR, P25, etc. We selected DMR as it is the most cost-effective and feature-rich, and solves more of the common two-way radio limitations. The two-slot operation eliminated most of our channel contention issues. I suspect it might also reduce the total number of repeaters placed in operation in a region since two separate groups can have their own private slot (instead of building yet another repeater on a different channel). Also promotes greater cost sharing (repeater and site rent costs can be evenly split between the two users groups).
Can't beat the audio clarity. The voice quality is really determined by the design quality of the subscriber equipment.
The high-elevation repeater is operating in "Dynamic Mixed Mode" (DMM)" so it switches between analog and digital automatically. This maintains some backwards compatibility with legacy analog radios. We setup the DMR radios to auto-scan both the analog and digital, or run automatic mixed mode on the subscriber equipment so it can decode either.