Quick and dirty tentative result:
Looking at the edge of the frame, the black outer masked part it, looks (SNR as measured in Iris) better than the 5D3 and perhaps even a trace better than the 1DX (5.0 vs 5.3 ADU and 6D also has just a trace more MP) but not close to an Exmor. It might have about the best DR at low ISO that Canon has made so far, maybe about like the 1Ds3. Seems like the 6D,1Ds3,1DX will be Canon's best for low ISO DR most likely. Still a far cry, from Exmor/Aptina/etc., as expected. Rough results though, sometimes the main frame is worse than the masked area, that didn't seem to be the case so much for the 1DX but was for the 5D2/5D3 so perhaps the 6D might end up a touch worse or the same instead of a touch better than the 1DX, probably doesn't realistically matter too much either way.
So not a bad result by any means but hardly cutting age in this era.
It is a bit of a shame that they could not have at least given the 5D3 at least their best effort if they can manage it in the cut down low cost model.... the 5D3 they actually gave a bare trace worse DR than the old 5D2 at low ISO (better at high ISO though). Pretty weak that the 6D will have cleaner low ISO and basically the 5D3 will have the least clean low ISO DR of any body release for the year. That said the 6D is definitely not using some new uber line, not that I expected it, so it's not WORLDS better than the 5D3 in this regard by any means, but it does seem like it will be better and just enough to be noticeable in the real world, looks like you will be able to push it a bit more. At least for low ISO, the sensor seems like it is probably modestly better than the 5D3 sensor.
Doesn't make their 5D3 effort look like they tried so hard and if they can do better in a cheap model then it means they could have done better in a pricey one.
Hopefully this is not off of the rumored new process line otherwise they will still be far behind Exmor for years it would seem, but I bet it is more just a modified 1DX line. Maybe the 7D2 or the new high MP FF later next year uses the new line??? assuming that there really is one