I'm sure that over the years they have blueprinted the structure down to the last detail so that it can be reconstructed in exact detail. When tourists walk past, I'm sure they won't just turn up their noses and say "pff! Those aren't the original shingles!"
-k
One thing they just don't have anymore are trees big enough to replace the 800 year old oak beams that were the major fuel source for the fire. However that stuff was up in the attic which I don't suppose tourists ever get to anyway. I'm sure they can recreate the exterior to make it look original.