The castle did not play any significant part in the battle, it was well behind the allied battle line. I believe that the armistice was signed there, and no doubt Napoleon would have spent a night or two there, as it is the most impressive building in the area.
Our battlefield tour included an evening meal at Austerlitz Castle, but we were not expecting the artillery drill display that went with it. Jan even got the opportunity to fire the gun. Next came a display of sword fighting and finally the meal itself.
An excellent evening, and a very enjoyable addition to the tour.