In terms of patients' rights, very, very little is guaranteed in the Medicare Conditions for Coverage, or what you might call "law." We've spelled out the specifics in the "Rights & Responsibilities" module of Kidney School (http://www.kidneyschool.org). The ESRD Network folks were very helpful about reading that module and helping to make sure that we didn't miss anything.
Most aspects of a protocol or clinic rules are up to the clinic to decide, and as you've seen, they can differ quite a bit. They can choose to do contracts and require that you sign one if you want to dialyze there. Personally, I am not at all a fan of the "home dialysis is a privilege we can take away" approach. Since when should better treatment be a privilege, and if they can't get along with you at home, what makes the centers think that you'd be easier to deal with when you're there three times a week? I am also not a fan of behavioral contracts, as they seem very controlling, and the exact opposite of a patient-centered approach.
IMHO, dialysis needs to be about helping folks to live as well and as fully as possible, and on their terms as far as is possible. No-one chooses to have kidney failure, and having conflicts with the staff and needing to battle to get your way is linked in research with lower physical and mental functioning--and a higher risk of hospital stays and death. Research also supports that the more autonomy (control) people can have over their lives, the better they will take care of their health problems, and the better they will do. A controlling, contract-based approach is the exact opposite of what's best for patients.
From what I've seen, some clinics do an excellent job of being patient-centered. Rubin in NY, the University of Indiana, and Northwest Kidney Centers in Seattle come to mind. In large companies, centers can vary quite a bit depending on who runs each one--there are some terrific ones and some that are more controlling. The trick for the next few years is going to be to identify the best practices and spread them so more clinics are doing what works best.