Is that new? Because SpaceX has streamed launches on YouTube for years.
I tried signing up for twitter but gave up at the "match these dice with these symbols (1 of 10)" stage.
It's not a great interface compared with youtube etc, not rewinding etc, but at least it works
Looking at the SpaceX feed, they seem to be using whatever tech they got from the Periscope acquisition (at least the servers were still pscp.tv).
So take with that whatever it means, that it's just not going to be as first-class citizen like in Youtube. But the CDN etc must be good enough as those things are easier to do nowadays.