No, oil based paint would not have done that. I would have peeled right off. It doesn’t like moisture behind it either.
It sounds to me like you need to remove the plaster and build a stud wall inside the building with a moisture barrier on the exterior side of the wall and the inside sealed with Drylox or similar. Also you will want to tuck point the outside of the bricks and seal those or find any leaks that you have and seal those.
Henry in MI