As I am writing this, the GUADEC is taking place in Paris. And it is broadcasted live over the web using WebM, in other words the Matroska technology.
For a long time, basically since Matroska was designed, we made sure that Matroska was not only suitable for file storage but also for continuous/live streaming of video. Some video players like VLC may already support this, but it is really becoming a reality within web browsers.