The AI has to know about the environment. So it needs to know what is actually classed as cover. I'm no AI expert.. hell I'm not even an AI beginner, more like an AI NOOB! but this is my (untested) theory (logically it should work, or you could mix this with A* to get the desired results)....
Let's say you have a PLAYER sprite, an ENEMY sprite, and also a WALL sprite (the cover). What I would do is have SAFECOVER sprites (dummy sprites) around the WALL sprite (all 4 corners and all 4 sides I think - maybe too much?) and have each of them fire off a bullet sprite (dummy sprite that has bullet behaviour) towards the PLAYER. If the bullet sprite hits the WALL, then that is flagged as a good cover position, so move onto the next SAFECOVER sprite. If it hits the player, then obviously it's not safe there, since the enemy can see the player, so therefore, the player can see the enemy. After checking all SAFECOVER sprites, cycle through the enabled ones (good cover) and maybe randomly choose which one to move the enemy towards so it seems less robotic.
If I was to do that kind of game, that's how I would approach it. I'm sure someone can come up with better but since no one has yet offered any suggestions, I thought I'd throw it out there. I have thought about this problem in the past Good luck!