I used to dispatch for UC Air Care. They only used the outerlink satcom stuff when they were out of range of the UHF or MARCS. MARCS was the primary, and it did not work very well either. I cannot imagine using that for primary communications without major upgrades made. UHF was mostly used by services coming into the Cincinnati metro area that didn't have our MARCS talkgroup. The two were patched together on the console all of the time however.
Also then, Christ didn't have radio communications at all for air. We had to relay by phone to the ER or mostly the Cath lab any patient report if needed. I surely hope that changed.