I have to add something to my post:
Phase One does it this way (pdf). They practically do an option c) which is: separating green from red and blue into two overlapping "layers" to reduce the gaps in pixel density and as a result can use method a slightly different method a) to bin the pixels. Considering, that the pixel-density of a fullframe-sensor at 45mp would be at least double as high as on a medium-format p45+ sensor, so it might even be possible to use this method whithout rotating the green-layer.
Another Example of how it could be done is shown by fuji's exr technics. Here it's basically another arrangement of the color-array to do 1:2 binning called pixel fusion. The article linked explains it very well.
I guess at the end, the only one who can give a real answer on this issue is canon itself - but even regarding registered patents by canon does not really deliver any clear answer at the current time.
Thanks. These are the best information that I have ever run into. So far only Fuji and Phase one officially claim the pixel binning. The Panansonic webcam is a totally different animal. the phase one article brings out some very interesting point. when doing a 4 to one pixel binning,the resolution actually decreased to by a factor of 16, due to the over lapping of the binned super pixel. Phase one does not claim the resolution factor. It just says better than 16. From my point of view. Fuji sensor is deigned to be pixel binning. Phase one is kind of a stop-gap. The other point and shoot low light setting may be nothing more than the downsizing of the picture to average out the noise for the pixel peeper to make the picture looks good. Let us face the fact. Pixel binning is a BIG deal. I doubt that Canon or any other camera maker will hind such a BIG selling point from the public.