How is that even possible? It's in direct contradiction to:
§ 121.629 Operation in icing conditions.
(b) No person may take off an aircraft when frost, ice, or snow is adhering to the wings, control surfaces, propellers, engine inlets, or other critical surfaces of the aircraft or when the takeoff would not be in compliance with paragraph (c) of this section. Takeoffs with frost under the wing in the area of the fuel tanks may be authorized by the Administrator.
There's no legal basis for the FAA to provide any other alleviation. Unless I'm thoroughly misunderstanding that section.