Cheating or Not Cheating?

Thomas brought this to my attention, but I wanted to throw it out there. At Columbia, there is a course that all students are required to take -- Literature Humanities -- which is taught by different professors (there are 57 sections). It is a survey course and there is a course-wide exam given at the end (basically to the entire first year class). The exam asks students -- among other questions -- to identify quotations from the various works studied. One professor came up with a study guide which listed the quotations that were to be used on the exam. Students in this section redistributed the study guide to other sections of the class, which messed up the exam (to put it mildly) because students knew which quotations were to be used. The lead professor of the course found out about this "study guide," (initially she thought someone had stolen the exam) and has now decided to discard the exam results and allow students to either take the exam again in the fall or use their other grades to determine their grade. I think it's clear that the professor should be fired.
Was it cheating for the students to use this study guide? I don't think so, the provenance of the guide was legitimate, it wasn't as if some student was distributing it improperly. On the other hand, the students reading the study guide might have realized that the professor should not have been giving out this much information. Columbia does not require students to report academic misconduct. Comments?