University of Virginia does this as well:

"Out of respect for the founder of the University who did not have a Ph.D., University faculty are referred to as Mr. or Mrs. instead of Doctor, even if they have a Ph.D. Students and faculty historically addressed each other in this manner. Medical doctors are the exception to the rule and they should be referred to as Doctor."

http://www.virginia.edu/deanofstudents/studenttraditions.htm...