I can confirm that the AI has built an artillery unit, moved it to one of my cities and bombarded with it. This unit cannot be captured or auto produced but could have been upgraded from an earlier unit.
I would like to know what causes the AI to use its artillery. If the AI used enough artillery offensively, they’d continue to be a serious threat throughout the game.
I still think the most detrimental flaw in the AI’s logic is its inability to perform a competent amphibious assault.