I have never called ahead, but when a property is "sold out", it stands to reason the hotel will do what airlines do when they are overbooked: move their elites up. In this case, room categories. I was in Taipei last fall after one of the major typhoons came through. This resulted in the Sheraton being fully booked, and when I arrived to check in at 8:30pm -- without calling ahead -- I had already been upgraded to the Duplomatic Suite on the top floor. [And I was only a Gold at the time.]