Wallpaper removal is NOT an exact science. We do have many years of experience though, bringing it to as close to a science as possible. But even with our trained eye and experience, there is no way to know for sure just what it will take to get your paper down. Many factors play a part in how easy or difficult each paper removal will be:
Type of paper
Type of paste used
Preparation, or lack of it when it was hung.
Condition of the walls prior to the paper being hung.
Other layers of paper underneath