Very few streaming services seem to offer 50/60p streaming, even the big "premium" ones like Netflix and Prime, it's one of the things that really annoys me about them, especially when they're offering content like sport.
Netflix have the capability - their own test stuff is streamed at 60p. (Search for their test short 'Sparks')
I've not seen anything - yet - on Amazon Prime video that suggests they have a 50p or 60p workflow. I can't imagine they aren't considering it seriously now that they have so much sport.
Eurosport not running at 50Hz is incredibly disappointing though. It's almost as if they want streaming to be 'second class' compared to linear... (Like Sky presumably, for NowTV)