A last question, is it always the lens being calibrated in relation to the cam, or both ways? In other words, if you have two cams one front-focusing and another back-focusing with the same lens, can the cam-lens calibrations get everything in line, or is it either one cam or the other...
As I understand it, when Canon 'calibrates' a camera and/or lens, they do their best to set the baseline to zero on everything, rather than specifically trying to match lens to body.
As to the lens being sharp throughout the focal range, that depends on the lens. Generally, zoom lenses are sharper in some parts of the focal range than others, due to the design of the lens itself - I don't expect that calibration would change that.
I sent my 35mm L in to Canon CPS because it took a MA of +17 on my 1D MK III. The technician added a note that the lens was installed on their reference 1D MK III and set for sharpest focus.
I have found that the AFMA differs by body, so they did their best to zero it out for a 1D MK III.
It was back in less than a week, and much better at a AFMA of 0.