We both agree that the professor should have made his own questions. However, this does not get the students off the hook. They used a resource where the publisher clearly says: students, do not use this to study. So, this is clearly, without a doubt cheating. I'm sure that many students knew the professor would use the questions verbatim, making it even moreso questionable.

What if someone came up to you and said "here's a test bank man, the prof pulls the questions right off it!" Clearly it is unethical to study from these materials. Similarly, if the test bank merely says "STUDENTS: Do not use this to study" then it is also unethical to study from.