Channels don't exactly exist, but you can programmatically create topics within streams. Sometimes it gets to be overwhelming, like out GitHub bot that posts every PR for every repo under its own topic within the GitHub stream. It's definitely a new way of thinking about chat, and there's a learning curve of about a week, but so far it's been fantastic.

I've used Slack and HipChat previously, and AFAIK the integration methods are all roughly equivalent - post a message to a URL with a token.