Steve,
I'm a fleet mechanic. I currently work for a local municipality in Illinois. I don't know how well private institutions maintain their fleet vehicles, but I do know that municipalities go by regularly scheduled maintenance. I was a dealer mechanic in a past life. I feel that if you purchase a fleet vehicle, you are getting a vehicle that received it's scheduled maintenance. This work is performed on a strict schedule. A good question is, "Was the vehicle abused?", well.... don't you ask yourself that when you buy a vehicle from a dealer? At least with a fleet vehicle, you know that the regular maintenance was performed.
That's about all I can tell you about the subject. You must be an educated consumer. I have given you the most honest information I can give you.
These are man made machines that are destined to fail, at one time or another. Cars always break-down. Choose one with fewer miles on it, and one that has been maintained.
If you would like to purchase a municipal vehicle, search your local municipality's web page, or call them for auction dates. You can get a vehicle priced under market value if you play your cards right.
GMdude