Assuming this is by design, but publishing a Twitter link does not display the oEmbed version of the Tweet — just the URL. Live-blogging is often a report of current sentiment, and being able to use oEmbed would be a useful feature.
Liveblog uses a Custom Comment Type, so you’re effectively posting a Comment when using the plugin; it just does a lot of other nifty stuff as well!
Evan Solomon discovered that oEmbed doesn’t work with Comments, as it does Posts. Now I haven’t tested it out, but you could try enabling his plugin, and see if that solves your problem?
I agree though, it would be useful if they could work together! 😀