You've got it backward; all the other sites are subsidizing your unlimited (but site-restricted) streaming.

Here's how to do something like BingeOn right: work with IETF to define a QoS flag that indicates streaming video, allow customers to opt in to throttling of that flag, then make sure everybody knows that they don't have to coordinate with Tmobile -- any provider can use the flag, and any carrier can honor it. Finally, the carrier could put an icon in the phone status bar (or an LED on a hotspot) indicating whether the current video streams are throttled and free.