I think it's safe to say a fabulous way for AI using Artillery is here.
A few things I noticed on Enslaved / Captured AI Artillery (both work really well), and the combination of the 2 should make for a refreshing game.
If AI Artillery that has been enslaved does not have any defence points, it will usually try to get to the closest city. This probably happens, because 1) the unit needs a defender, and 2) the AI will always try to bombard no-defense units first (and will destroy improvements, etc in the process). So this is a good thing.
If the AI on the same turn where an AI Artillery has been enslaved/captured, decides to make that unit a defender of that AI Artillery, it will probably stay in the field and bombard from there.
If the AI Artillery has defense points (as Kirajara's did), it will not necessary rush to a city, but may just hang out and bombard. The AI must know it has defense, so is okay with the unit being out by itself.
Both enslaved, and captured artillery's work pretty darn well. Within 15 turns of testing in the middle of a game, I saw alot happen.
Lot of units were at the front. and each side (purple and blue) had about 15 units that could enslave artillery.
Purple slightly stronger. All the arty they enslaved (6 of them), they moved back to their closest city. I was a bit worried at first. Then I saw them a couple turns later bombard units in the field, and then changed to bombard an enemy ship a couple squares out (seems ships have a high priority to be attacked). Then several turns later, after some reinforcements units arrived, 4 of those artillery joined up with 4 units, and started immediately heading out towards an enemy city. This seems to be what is also happening in Kirejara's screen. Only the stronger side (purple) with more available units did this. The weaker civ (blue) did not, it kept it's units stationary, and bombarded from there.
Blue side enslaved about 5 artillery. They moved 2 artillery to a nearby eastern city. 1 has not done anything, the other moved out of the city to bombard a nearby enemy city. I noticed them bombarding a city one turn, then changing to bombard a unit in the field the next. The others went to another nearby western city, and bombarded units in the field, when they were within range. One stayed on the front.
I suppose what may happen, is during Peacetime or even wartime, built artillery have no target, and may get 'stuck' in some kind of no target mode. If enslaved during war, or captured during war, they seem to be set to their active mode. If war ends, not sure if those artillery still work or not. I remember from early 'barb arty capturing' tests of the first CoMM3, that they were active for a while, but I think if peacetime hits, they may become non-active.