Unfortunately I own a camera with one of the worst sensors ever made - the 5D2 (if you believe the DP review forums - yes I know, I've already gone blind!), but I have never seen the pattern/banding in the shadows - -where is it?
Seriously, I've never bothered with this sort of stuff before, I just take photos, but I was curious to find out if there was an issue that I should be aware of so that I know how to work round it. I took a shot at 100ASA that included a decent area of deep shadow that included picture detail (brick wall and foliage) and then manually exposed the same image deliberately underexposing 2, 5, 7 stops etc., something I would normally have no reason to do. Looking at these at 100% in DPP and pulling up the brightness as far as it is possible the only pattern at 2 stops under was the mortar lines in the brickwork and not really any noise; pulling up 5 stops there wasn't much detail left, but no real noise, pattern or otherwise.. Then took the same shot at 3200 with full exposure - shadows show some chroma/luminance noise, as you would expect, seen at 100%, but no specific pattern/banding. All raw BTW. Lens was CZ35/2, but can't see how that would affect result.
So in what circumstances does this phenomena manifest itself, or could it be there in some bodies but not others, i.e. a manufacturing/calibration fault.