In the rate instance I don't have sprint connectivity, I roam on vzw...
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There is a misconception that all Sprint devices roam on Verizon when they dont have service but Verizon does and that isn't the case. That is only selected markets and in most cases is voice only.
You're fortunate that you live in an area where those agreements are in place but most people don't.
Also read the fine print your data roaming is limited to something like 300 MB as I recall so you cant depend on it too much.