So these trespassers are untouchable?
I can just occupy a house that is vacant and no one can tell me to leave?
It's been known to happen. Of course there are many different rules depending of jurisdiction but in the rust belt this has happened more than a few times. Many owners who live elsewhere have not checked in on their property, meanwhile, someone moves in and "owns up" the upkeep. They get utilities from the company, claim they are the owner no matter who is asking and after some time when finally faced when getting the boot they claim their owning up of the property makes them the owner of the "abandoned" property. Happens more against private owners than it does with banks, courts don't like to disagree with banks of course.