As far as I know, there is no divisional artillery in the game. We do have regimental artillery, but none of the regiments in the demo have them on either side. The game models each gun separately, so a battery of 6 guns actually shows 6 guns when fully deployed.
At Waterloo, D'Erlon's corps actually made it to the ridge, driving off at least some of the defenders. They were advancing against 3 batteries, two on their left and one on their right, none in the center. When the British cavalry attacked, they were pursuing elements of D'Erlon's corps all the way back to the French lines. The French grand battery probably didn't have clear shots because of the retreating French troops. I think in the game the artillery would go ahead and shoot anyway.
Mercer's journal mentions being charged several times and he disobeyed the orders to retreat the gunners into the nearby squares. The cavalry never got close enough to attack the artillery.
I think artillery crews taking shelter in nearby squares will be part of the British AI that has not yet been written.
Hook