I honestly wouldn't be surprised if Aramark also did food service for Congress. I have no knowledge of who their food service provider is (or if it's insourced) but most of the food service providers will do food service for pretty much any organization that will pay them, with the quality/level of food service that the company or governmental organization wants. It really doesn't matter if Aramark also happens to cater the prison system - Aramark will happily provide whatever quality of food is desired on board as long as the proper funds are exchanged to allow for that quality of food. If Amtrak food is as bad as prison food, then that's a problem with Amtrak's level of funding to Aramark, not the fact that Aramark is the supplier.