I didn't apply anywhere else, but seeing as I had basically zero contact with the school during my deferment, I betcha they wouldn't have known if I had applied to any other schools in the meantime. Moral or not, smart or not, that is my feeling.
If I had called to tell them that I would not be attending, my guess is that they would have happily taken my deposit money and given my slot to one of the 100+ people on their waitlist. Every time I called the admissions office during my deferred year, they basically had almost no clue who I was or that I was deferred.
Just my $.02