Transport Canada uses Working Note 4 as the basis for certifying CAT II Autopilots. That requires a minimum demonstrated capability of 15 kt Head/15 Kt Cross/10kt Tail. In reality these are the minimums & most manufacturers will try to get the highest wind conditions they can - bearing in mind that one failure (Excess Dev) & you're back to the drawing board as you have to demonstrate a 95% success rate.
If memory serves for CAT III, you get 50% of whatever max winds you demonstrate a successful (read no Approach Warnings) landing in. By coincidence we did the final CL65 HGS testing at St. John's and I remember winds well above 20 kt in less than CAT III conditions (and waiting while a scheduled service came in - "No RVR available").