Yes you can certainly stream and do message passing within HTTP (for some browsers) but you can't, for instance, return headers more than once without your own application protocol.

The most interesting bit about this architecture for me is the 1:1 mapping with a pure HTTP resource. It's a bit like an implicit subscription to a pub-sub enabled resource. In this implementation we are simply calling our API like we normally would (except on the stream domain) and waiting for an update.