In some characters' powerstyles, there are some powers with the following line:
aicanuse = false ;
This means that when the character is being controlled by the game's AI, he will not be able to use the power. If you remove it, he will be able to do so.
Also regarding the game's AI, you can set up the situation when the AI will use each power through the aitype
line, you can find more info about it here