This is the outcome of Project Drake, started a year ago. Surveys were conducted, with the data going into OSM. The data is rendered to a custom style loosely based on a previous non-OSM one. There is a database of the OSM data to support street name and third-party location searches and a database of institutional contact details. The two are loosely linked using the ref tag so that the university database can determine where an institution is located geographically. There is an API; and a separate presentation on small screen devices.
A paper map is also in final draft form.
There is some background the project here: http://www.openstreetmap.org/user/davidearl/diary/15398 and here: http://www.openstreetmap.org/user/davidearl/diary/17050
The University's Computing Service has published a news release, here: http://ucsnews.csx.cam.ac.uk/articles/2012/09/24/new-university-map-launched
The University is intending to redesign its web pages from the end of the year, so the styling will change again before long.