Think about how many times outside of peak you've ever interacted with an HR person, saw one, or even needed one. I've seen ours outside of peak maybe twice. I can't even remember. All it takes is some delegation from the Center Manager to put a few of his responsibilities (holy crap, managing!) onto an ORS or two to take some heat off if it's a lot of stuff going on that week, otherwise the HR stuff would just be an extra few minutes to his week.
Nowadays most of the HR stuff could be done on the computer/telephone. The new hire goes through the process of application online, sends off whatever stuff, then gets a UPSer password and a phone number to call. They call the phone number, get any contact details they need to call the center or go for testing (blood or physical), then come to work for whatever shift they're supposed to be at. It's pretty simple, really.
Outside of peak season I don't see the need for maybe 1 person for HR duties for most of a state. There really isn't much that they have to do seeing that we don't work in an office environment, we have a union that does all the bickering between management/us, and outside of 3 months of the year they're basically getting paid to sit and twirl. It's a great money saving move by the company.