Half of the time I use the privateer bomb attack with a 100% chance of making fire traps, no traps are made at all.
The language on the card for powers like "The Big Guns" has a little clue that may help you, "100% chance for Fire on enemy tiles." Although it's not immediately visible, each battle board has areas that are your team's side, neutral ground, and the enemy's side. Try aiming your Big Guns on the enemy side of the battle board, and you'll see better results.
Thanks for clearing that up. I thought enemy tiles meant tiles that were occupied by an enemy (the one an enemy is standing on). I can guess how it might work in ship battles, your ship, their ship, and boarding planks being neutral. Is that right? what about land battles? Is the neutral area about the same size as boarding planks? Smaller? Does it change size on different battleboards?
Unfortunately you can't and each battleboard can be set up differently. (One thing is for sure, you will be able to tell you're on enemy ground if your Pirate talent activates.) Sometimes the back enemy line is very narrow and sometimes larger. The easiest place to tell (and the perfect example) would be during combat aboard an enemy ship. The enemy ship is their territory, the planks are neutral ground, and your ship is your territory.