I've done some tests with 1.2.1 firmware and it seems that the HDMI out is in fact 422.
I'm a bit surprised the author of this site seemed to imply canon was publishing untruths in regard to this.
I recorded to the Ninja 2 and compared footage with internal footage using scopes (FCPX) and also 300% crop on a red coloured object. With the 420 internally recorded clip, the red edges are jagged and stepped when viewed at 300% crop. The prores image from the Ninja 2 at same crop is smooth. Also when viewed with luma waveform and vector scopes, the internal recording shows cross hatching in some areas where as the Ninja 2 recording does not.
Looking at the 422 vs 420 clips side by side at normal resolution does not show a lot of difference.
However one of the main benefits of 422 is more chroma information than 420 - footage won't degrade as easily transcoding between codecs. This is one of the reasons some broadcasters stipulate 422 as a minimum requirement.