Online video site YouTube will be partnering with the live video streaming service UStream for YouTube’s live event on November 22, an anonymous tipster tells us. If true, the ramifications of the partnership are interesting for a number of reasons, most significantly the potential for a YouTube live-streaming service.

Here’s what we know: YouTube’s event, called “YouTube Live“, will feature popular video bloggers, famous musicians, comedians, athletes and more, all gathered together in an outdoor pavilion in San Francisco. In terms of coverage of the event, we received the same official line from YouTube as Silicon Alley Insider got a few days ago: “We’re working with a third party to live-stream our event called Live. We have no product to announce at this time.”

That third party, according to our source, is Ustream.

More interesting is the rumor that YouTube could use the event to launch a live-streaming service of its own. If that is true, it seems unlikely that YouTube would go to all the trouble of partnering with Ustream for the event if it’s just going to launch a product that directly competes Ustream at the event. Instead — and this is speculation, as our source refused to confirm or deny this — perhaps YouTube will announce a formal partnership/alliance with Ustream to handle live-streaming on YouTube.

There was talk earlier this year that YouTube wanted to get into the live-streaming business, but more recently, the thought was that it would be too expensive an endeavor for now. If the video site seriously wanted to get involved in the area, wouldn’t it make sense to partner with (or acquire — again, speculation) a company that has already been doing live streaming for quite some time?

While YouTube only gave us the comment above, we’ve also contacted Ustream about the rumor, and we have yet to hear back. We’ll update if we do.