That's why colleges collect bids and sign exclusive agreements with food service providers. I know that when I worked in dining services, while I had a right of first refusal, in over 10 years, I never used it once. Why, because in most cases, the contract didn't really give me that option. In most cases, my contract for the summer months was written differently than for the school year. In order to keep the dining halls open, I passed on more of the expenses to the administration.
Some contracts work on a fee basis during the summer.
You pay for the services plus a fee to the company. Also, keep in mind, that many times dining services does have staff around during the summer, cleaning and getting ready for the fall. I would be surprised if you couldn't find a local catering operation that would love to come on campus to provide you with meals.