This is from my 17-55mm at 55mm, stopped down a stop:
This is from my 70-200mm at 189mm, wide open at f/4:
Both are processed through Phase One Capture LE with no output sharpening. I didn't adjust any of the settings from the shot defaults. The top photo is a flash capture indoors, and the bottom is a sunlight/shade shot outdoor. I used a 1/250s shutter speed in the telephoto shot (plus IS), and I shoot on an APC sized sensor (Canon 20D).
I'd informally judge them to be about the same sharpness, but the bottom shot was a relatively rare find among my telephoto shots. Perhaps I tend to use the telephoto more often for 'action' shots whereas the shorter focal lengths get more use in controlled lighting situations (i.e. studio/flash). In any case I think it speaks to the need to take time to ensure sharp results from long lenses - the original point of the article.