Propes can say more about Icecast, but I know Shoutcast will broadcast any input stream and I would assume Icecast is the same.
That thing should work; it is the same sort of device as the Voiceport we have been using. Plug it into the mic jack on your computer and configure your webcast software to stream that input out to the internet. You should be able to stream it without saving it to a file, although you would want to so that you have an archive of it.