I e-mailed the DEC to clear this up and asked if there are any restrictions for camping above tree line during the winter months since Part 190 doesn't mention anything about snow on the ground. It just states "EXCEPT" for an emergency or the dates listed (when winter rules go in effect) and never mentions any other rules for these exceptions.
Part 190, as quoted by the DEC...
http://www.dec.state.ny.us/website/regs/part190a.html#190.3
"d. EXCEPT in an emergency, OR during the period December 15 to April 30 each year in the Adirondack Park, or during the period December 21 to March 21 each year in the Catskill Park,
No person may camp on lands under the jurisdiction of the department which are located at an elevation in excess of 4,000 feet above sea level in the Adirondack Park or in excess of 3,500 feet above sea level in the Catskill Park. "
It says nothing about snow or any rules for above tree line during winter season or for that matter, for an emergency. Not a loop hole, not a trick, not a miss understanding, not an interpretation. AS written it says you are allowed to camp during winter season under any condition, these are the only exceptions.
Perhaps as a conservation minded camper, you might want to impose a personal restriction to a foot of snow so as not to damage the delicate environment. This is what i was taught and respected in my 40 years of backpacking.