The only roaming that sprint can do on verizon and vice versa is 1x roaming. Yes, you're still on the internet but the speed is maybe 2x dialup speeds. As far as EVDO, they do not have evdo data roaming agreements, and I don't think they ever will. As far as that cards, the cards themselves are programmed to communicate with a specific set of towers based on the PRL it's given, this is hard-coded. You technically could activate a verizon card on sprint and vice versa but it's up to that specific company to be willing to activate it on their network. Once it's activated on that network though, you can't use it on the other network at that point unless you activate it on that network (much like a cell phone, it's on activated on verizon, it's a verizon cell phone and vice versa). All the connection software does is tell the card to initiate a data connection, the card itself controls which towers it communicates with and what network it's on. If you don't believe me, look it up.