I've been working with emergency preparedness/pandemic preparedness consortia lately. The Feds require sat phones as the 4th level of communication. In test runs using the sat phones that a few agencies have and testing some of the sat phones the hospitals use, we found connection rates between <30% to almost 80% of calls being completed. Only 2 companies over sat phone service and neither could promise that call would be completed.
Where I live there are times that no satellites are usable, so the phone is useless until a satellite comes in range again. I used to love the thought of sat phones, they would be great if they worked.