Rebbe and scoot - I fully appreciate your comments. I think, however, that GradSM's post may have been written in a tone that the poster does not use when communicating formally or directly with the rest of the team. My reading of the OP is that this issue has caused concern and not inconsiderable discomfort, but has yet to snowball within the production context.
GradSM, I have been in similar situations. Granted, when I worked as a student PA, it was in a city where parking is affectionately referred to as HELL (read: Los Angeles). After I raised my concerns - quietly, gently, off-line - with the Company Manager, he looked into finding me parking. What we came up with was a limited parking pass - I could park on any levels that had "blue zones," meaning stairs-only access. While this did mean that I had to schlep up the stairs each time I left the theater on an errand and again at the end of the day, my car was closer than it would have been had I used the closest free street parking (which was a mile away, across a major boulevard). The limited pass was also, from what I understand, considerably cheaper than the other passes.
Here's a little brainstorming: if you are being reimbursed for mileage... that might be a way to work out a compromise. How about ditching the mileage and getting a fixed stipend for parking? Unless you're commuting 60+ miles in a truck, chances are that this will be a little more than the gasoline, but won't sound quite so much like kvetching about nickels and dimes.
I would strongly discourage you from making any threat-like statements... you are a student, and may be associated with this regional company directly through your school. Throwing around ultimatums will NOT earn you points, and may very well damage your prospects with the company and in the program at large. As a student, you are also probably receiving some form of financial aid or grant/loan monies; if the regional company does not have the protocol or resources to cover your parking, you might check in with the counselors at your school about scholarships for students who are working in the field. You never know when some $500 Rotary thing will show up.
Regarding scoot's comment about contracts - yes, do always read it. Twice, at least. I try to find a hard copy for my files, and, if possible, an e-copy so I can search quickly for terms if necessary. The glitch with this can be that many organizations do not have a cut-and-dried PA contract - it's pretty much whatever they need you to do, and unless there's some special agreement, the only official paperwork you'll get, ultimately, is a W-2. Questions about parking, travel, gasoline, food, housing if applicable, should all (always!!) happen in the interview.
Let us know how this is resolved.
Best,
Meg