The only thing I can remember is sometimes they change black out dates for AP once in a blue moon and is typically way ahead of time. I know they did that for Kong. Other than that, Universal is consistent in their hours. If there is a private event happening I would imagine they'd know well ahead of time, because I never seen their hours suddenly change, however I could be wrong.
In order to prevent change they might schedule certain days to reflect if they may have events, not just certainly having an event. As for example, there are certain times / seasons in which there will be times where Universal closes relatively early, but have another park open later and vice versa. Typically, that's due to having an event / due to the slow season. I do not think it's impossible to think that Universal not only closes early for a definite event, but also in case an opportunity springs up.