Quote Originally Posted by Cras
has anyone tried to use the towers when the enemy comes out of the city?

do they also shoot at units on the ground instead of on the wall?
If you order your towers to halt just before they dock alongside the walls, you should see them fire downwards at enemy units that are on the streets (not the walls). From this, I'd assume that if you're towers were in the right place, they should be able to hit units leaving the settlement gates.