I really wouldn't risk it, especially in Bosnia. The landmine situation is very real there, with around a quarter of a million still around. Most abandoned buildings there are abandoned for that exact reason. But if you're still looking for legit squats in the Balkans I recomend ROG, it's an old bicycle factor in Ljubljana, Slovenia. It's in the center of downtown, easy to find, and they don't really have much trouble from the police.