The roaming agreement for the Starbucks hotspots is 5 years, however its for people paying for Hotspot use.
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On the Tmobile website, Starbucks hotspots now show up as "Roaming HotSpot
(Additional charges apply)". Or at least they seem to be. It used to say what they were, but now they don't show a name, just a location. I think it's the Starbucks that are grey.