I get accomodations, including some testing accomodations, for a physical disabilty. It's not exactly what you're asking about, but I'd be happy to share my experiences if you wanted to PM me, and some of it might be applicable to your situation.
I do know that policies vary a lot from school to school. At Jefferson, they are more familiar with LD issues than physical disabilites but could do better about both. There is a whole process and criteria including providing relatively recent and thorough evaluation.