It's uncompressed 4-2-2 guys.
I'm finally getting it to work with the Blackmagic HyperDeck Shuttle and it grades amazingly. Noise grain is finer, there's obviously far less compression going on via HDMI. There's also about a stop more dynamic range and a more gentle roll off to the highlights. Amazing stuff.
If you get this camera, I recommend you shoot via an external recorder.
Now here's the proof... (blown up 200% in PS)...
More detail too - look at the thread on the outer ring of the Iscorama... Thread lines visible in the ProRes and smudged in the H.264 internal recording at 24Mbit.