I saw one last year too. I think it was on allears.net...might still be there.
We were there last year from 11/15-11/25. The resorts were decorated first and then the parks. The MK was the last and we visited it the am of the 25 (Tuesday before Thanksgiving) and it was decorated. I think that was ahead of the schedule I saw...I remember being surprised and delighted to see it.
As CindyBella said, the work always seems to be done overnight which makes the effect that much more special.