As far as I know, in order to get RSS in real time (i.e be pubsubhubbub subscriber) , the one who generates the RSS feed, must be a pubsubhubbub publisher, which means the RSS feed must include a tag which includes the HUB address.
However, there are lots of RSS feeds (published using RSS 2.0 only and not pubsubhubbub) which I can subscribe to via Feedly.
How is it possible?
Thanks,
Qwerty
So, Feedly does use PubSubHubbub, thru Superfeedr (and other hubs, such as Google's or Wordpress).
Fir the feeds which do not support PubSubHubbub, Feedly polls feeds at regular intervals. You may want to check this other question for more details.
Also, please note that Superfeedr can also be used as a "default hub" which works even for feeds which do not support PubSubHubbub.