The "charging yourself" thing I'll never understand. It's robbing Peter to pay Paul. What's the point of university units charging other university units. It's weird.
Actually, this is the logical way to do it, and many large corporations follow a similar type model. It is for efficiency's sake.
I work as a network engineer for a large corporation. Instead of allocating money for the network to spend, we are treated as a completely seperate business, charging the other business units for headcount, bandwidth usage, total number of servers, etc. It keeps us as efficient as possible, and ensures that all expenditures are completely justified.
Its kinda the only way a "cost center" (which parking enforcement undoubtedly is) can operate efficiently.
That said, in my years as a student, parking services was always a huge pain. You couldn't park in an empty lot for even 5 minutes past 6:30 AM (when free parking ended) without getting a $20 ticket.