As for elephants: I noticed them getting wild even if there are no defenders on the walls anymore. Even if the gate tower is ruined by onager fire. It wouldn't be weird otherwise. And the amok doesn't last very long... just enough to ruin your chances of getting into the city in an orderly fashion :)
The spy sitting in a city is supposed to open the gates for you if you're lucky... but somehow, it never happened to me, even if I had 50% chance of it happen. I don't even know how it looks like when he does that...
One thing I found very annoying about sieging: if you auto-resolve the siege, the buildings inside get randomly damaged. Even if you're not carrying any siege weapons, and even if it's farms and roads that get damaged. That is a damn bug if I've ever seen one!