I'm not sure how you'd get the internet from the broadband card to a router, but try a VOIP test and see how your connection is.
MySpeed VoIP connection test, VoIP test, test VoIP performance, test VoIP quality
VoIP Speed Test - Test your Internet Connection Speed | VoIPReview.org
VoIP Bandwidth Test
That third website says satellite at 400kbps can hold from 1 to 6 simultaneous VOIP conversations. But compare that to a DSL connection that can handle 3 to 60. Sounds like you might be able to do UMA. But kinda expensive when you can just go with Verizon.