There are a few 2008 NEC sections that cover deicing equipment:
210.8(A)(3)Ex. allow you to omit the outdoor GFCI protection if the receptacle is not readily accessible. This will keep Joe Homeowner from unplugging it and plugging his hedge trimmer or some other device into an outdoor receptacle without GFCI protection.
426.28 would require GFPE which is different from GFCI protection in that it’s trip threshold is about 30ma and not the typical 4-6ma for class A standard GFCI devices.
210.8 Ground-Fault Circuit-Interrupter Protection for Personnel.
(A) Dwelling Units. All 1 25-volt, single-phase, 15- and 20-ampere receptacles installed in the locations specified in  through  shall have ground-fault circuit-interrupter protection for personnel.
Exception to (3): Receptacles that are not readily accessible and are supplied by a dedicated branch circuit for electric snow-melting or deicing equipment shall be permitted to be installed in accordance with 426.28.