If that I understand that correctly - the professor used pre-fab questions from the publisher - then I have difficulty putting any blame on the students. That material is not a secret. It does not require subterfuge to gain access to the teacher version of textbooks. If you pull all of your test questions from such a database, then you are vulnerable to this.
I have taught one course as an instructor. I made my own test from scratch. The same is true for all of the classes I have TAed. Our department has a stated policy that using prior exams to study is fair game.
I took a stats class where our final consisted of questions from the book - and we knew this. I was going through the book while studying, saw a question and thought "That looks like one he'd ask us." and I figure the problem out. That exact same question was on the test. Unless there's some fundamental fact I'm missing, I consider that a similar enough situation to treat them the same.