What if you tried to move onto the tile the invisible unit is on, then would you see them?
No, but you would receive a message asking if you are sure you want to attack. Just as if you where to try to move your unit into the same tile as a normally visible unit from an other civ.
Except if you are already at war with the civ the invisible unit is from, then it will be an automatic attack! This can be problematic if you move transports around, as transports have a low attack value, they are likely to lose. So when the AI gets their hands on subs, always move the escort first and let the transport follow along the same path.
It should be noted that the message asking if you are sure you want to attack is an GUI safety measure, and since the AI doesn't use the UI, if an AI moves his unit into a tile occupied by an invisible unit, it will attack automatically and thus sneak attack, causing war, even though this may not have been the intention of that AI. when invisible units come into play, AI-AI diplomacy becomes next to impossible.
It is funny, the fact the AI knows the location of all units is one thing, but they should have been programmed to ignore this knowledge to act more natural. This isn't done very well, except for this one instance, where the AI ignores the knowledge as it should, but then Firaxis
still screwed up some way anyway, making the situation even worse....
