If data was binned in such a pattern:
R G R
G B G
G R G
B G B
I'd expect to see slightly more aliasing vertically than horizontally and very high resolution in both horizontal and vertical direction. Instead, we see a vast disparity in aliasing horizontally to vertical, with the vertical MTF responding to detail way beyond 1080. Horizontally, it's both aliased and soft measuring < 1400 or so out of the 1920. The binning scheme may explain the strong vertical aliasing, but it doesn't explain the low resolution + aliasing you see horizontally. And it doesn't explain the vast difference between horizontal and vertical, only a relatively small difference.
"binning" from the bayer pattern and you do get some aliasing, but it's hardly like the brutal aliasing we see on the 5D2, and it doesn't exhibit the wild cross color artifacts that we see either.
5D2 sensor is: 5616 x 3744, so the supposed binning would produce 1872x1872 image to be cropped / scaled to 1920x1080. Presumably to get the 16:9 aspect ratio you'd crop to 1872x1080 then scale, but that'd produce a very sharp horizontal resolution, but we don't see that.
Line skipping the 5616 x 3744 would lead to a 5616 x 1248 image, which would be cropped to 5616x1080 then scaled to 1920x1080. That doesn't explain soft horizontal resolution either.
None of the suggested theories fully explain the image facts. However, Canon marketing not withstanding, I reckon the line skipping does explain more of the visual appearance we see than the binning theory. There is still the scaling that occurs after either, and that is where I suspect more is happening. There also does look to be a demosaic stage in their too, from what looks to be visible demosaic artfacts, but they could also be compression artifacts - hard to tell. Binning would not explain demosaic artifacts should that be what they are.