Towers/gatehouse in siege battles

So I've looked to see if this is a 'not eb2' bug, and whether anybody else has mentioned it....perhaps this is a known bug on MTW2, but having seen no mention of it elsewhere here goes.

I am beseiging Thermon - -owned by Epirus - as Makedonia. There are some large Epirus armies heading my way so I assault the walls. During the siege battle the gatehouse and other towers are reigning their usual TW machine-gun fire at my troops. I gain control of the gatehouse and....no change, the towers are still reigning death down upon my men, and the gatehouse still shows as 'Epirus'. This surely isn't how this is supposed to work?