At my school, there's a website that has numerous free downloads of past exams (not affiliated with the school). The exams are a few years old and for certain classes, questions are recycled word-for-word. 😀 I've read in a couple syllabi that using any questions or something or another is against policy and what not, however, people are open about these exams, and nothing is done about it.
Also, these exams, as I've mentioned, are a few years old which means that they were handed back to students back in the day. Now, we don't keep any of the exams. We hand them in, and only receive a grade. If we come into to see the exam, we have to do it in the department and hand it back in.
If people are using old exams that were legitimately handed back, I think that it would be overlooked. On the contrary, if students were brave enough to use concealed recording devices to get the questions and answers, then it might explode into a huge cheating scandal. If it's the former though, I probably wouldn't worry, but don't take my word for it.
Plus if it's accepted that everyone is using old exams, continue to use them. They are an invaluable resource for learning the material. It's cheating if you somehow use them at the actual exam. Otherwise, it's fair game unless the exams/exam questions were obtained through illegitimate methods.