That said some a/c such as the A310 are certified for take off with frost over the wing tanks, which can happen if you land with cold soaked fuel. Canadian regulations require perfectly clean wings in any case.
Interesting!, but could you elaborate. Did you really mean "over" in that the ice was on top of the wing, or was the ice on the underside of the wing where it would be the closest to the liquid inside.
Also, what certification permits this? was it the design of the aircraft or the operation of the aircraft?