Actually, there is proof of this being real-time. There is another video out there where the developers are messing around with the tools of the engine and making changes to the demo in real time, such as changing the style of that old man's beard, and the color of the cult leader's beard, then continuing the demo at full speed with the new changes just a second later.
As for a personal bit of guesswork, I'm going to guess that this demo can run at 30fps on two of three GTX680 cards. Remember that the resolution of the demo doesn't looks like more than 1280x720, which is a very modest resolution for video cards like GTX680. Increasing the resolution from 720p to 1080p in that youtube window gave me no discernable change, and I have a pretty good eye for that sort of stuff.
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