With the automatic fire system, you dont have to start your fire by yourself. The AI can actually detect if you dont have your adrelanine rush. Example, your water can be mixed with gaz and will be on fire.
You can always have the "Fire Wall" option. With this option, you can manualy put your walls on fire or call the AI to make the fire. Some person are really excited about this option because you can have this on a normal house.