But the thing is, you generally don't just magically have the ability to seamlessly plop an ad into a part of the game. That kind of thing needs to be purpose built, to either have the option to plop an ad on the main menu + map, or to (more heinously) plop an ad ANYWHERE in the game.
So worst case scenario (well, not WORST because the game doesn't, like, go back in time to kill your grandfather or something) is that someone higher up said "Hey, what if we could put an ad anywhere in the game? Get the team working on that" and it was done... best case scenario is that I guess their games are coded so well that they can just seamlessly plop in a chunk of code that doesn't break anything else and just works?
But going off of past experience with Ubisoft games, that best case scenario is kind of laughable (insert a screenshot of the guy's face texture not loading for AC Unity here).