While RPI definitaly falls on the smaller side of the spectrum (~7000 students), we certaintly do a fair amount of A/V work in house and as such I feel compelled to comment.
The academic campus AV needs are handled by a division of the IT department, Media Ops. They are responsible for maintaining all the A/V equipment installed in classrooms and lecture halls. They also maintain portable sound systems for speeches and conferences, but the equipment is limited to some JBL Eons and Mackie consoles. They are also in part responsible for operating the CATV system on campus. They have both a full time staff and work-study students.
The various arts departments operate their own equipment for their performances in the various venues on campus. These are usually staffed with a combination of staff as well as work-study students. The equipment used ranges from D&B Q7's to powered Mackies.
The student union operates both a lighting and a sound organization that is responsible for handling all the student produced events on campus. The sound organization, which in part is my responsibility to run, owns and operates a number of sound systems ranging from an EAW KF650 system (hopefully with a Yamaha M7CL-48 out front next semester) to powered Mackies. The lighting organization operates similar to us, and as part of their larger setup they have a 48 foot box truss along with a 48 channel ETC Sensor Touring Rack. We handle typically 70-90 events a year and are completely student operated.
Both a 10,000 watt radio station and an on-campus TV station are operated under the Student Union and are completely student operated (along with some community participation on the radio station)
A/V requirements in venues on campus are typically handled through staffing of the venue or through the various organizations listed above.
Large events are typically contracted out to local production companies. (i.e. Graduation, etc)
As I've said, I'm only involved with the student side of it, so the portions of what I've said relating to the academic campus are only from what I've seen and heard. Considerably more could be outsourced from what I've mentioned.
For reference:
http://sound.union.rpi.edu/http://lights.union.rpi.edu/http://rpitv.union.rpi.edu/http://itops.rpi.edu/avservices/I hope at least some of this is useful.