Codeforces currently supports embedded Youtube and Twitch livestreams. Hacker Cup Finals is streamed only to Facebook, but I imagine there are lots of people who would like to watch it [or at least would like to know about it] on Codeforces. Unfortunately, it seems unlikely that Hacker Cup would be streamed to Youtube or Twitch in the foreseeable future.
It looks like embedding the stream is as simple as using an iframe, from the little research that I've done on this page, which is about a church for some reason.
I don't know how Codeforces implements this integration, but if it is with an iframe, it might be as simple as a third case to the supported stream link regex.
Why should Codeforces want to add Facebook Livestream support?
Because Hacker Cup is a big-name programming contest. If Codeforces wants to continue to be the place for everything competitive programming related, it would be good to support at least the major CodeJam Finals/Hacker Cup Finals/ICPC World Finals streams, since most competitive programmers are interested in them.
The direct payoff from Codeforces's perspective is that it's support for a major contest and something very beneficial to it's users. The payoff from Hacker Cup's perspective to use this feature is that it provides greater visibility and integration with the community of people who are interested in programming contests. It's clear that there's a huge overlap in Hacker Cup contestants and CF users.
What do you think? Would you like to watch the Hacker Cup Finals stream here?