Does anyone know if it is at all possible to break into the still abandoned buildings?

Er,
Its possible to "break into" just about anywhere. Are you sure you want to "break into" these places? You should know, "breaking into" changes the status of what you're doing from misdemeanor to criminal offence. You will come to realise that this site does not condone breaking and entering and that people are very reticent to reveal points of entry. Otherwise its a great place to learn a lot of stuff about urban exploration and a lot of other things.

Could you clarify that?

If the place is wide open, it's just trespassing (a misdemeanor?)

If you kick the door in, it's breaking and entering?