Fromt he games I have played :
Normal AI - Barely uses mines and when it does they are in extremely low numbers.
Hard AI - Uses mines often and in quantities from low to medium.
Unfair AI - Just needs to stop it. Mines everywhere. They even snuck some in my closet. I check the bathroom......you know what I saw? Mines? Yup, they were there too. I looked in the dishwasher.....you know what I saw? Mines? NOPE! BUT THEY WERE RIGHT BEHIND ME! COMING OUT OUT OF THE OVEN!
But seriously.....yes the AI uses mines.