Mangosteen has been fruited in the pavilion of Fairchild Tropical Botanical Gardens, but I would consider that in the same category as a greenhouse. It is well protected, and could easily be more sheltered more from cold dry winds if need be.
I'm going to give it a good try here south of Miami. Could be wrong, but our alkaline soil worries me more than the cold. My tree did well with our lows last year (high 30's). Landscaper is supposed to dig a big hole tomorrow, and I will plant after laying down a liner and filling with choice soil. Prepared to cover and protect the tree if need be, but the location already constitutes a nice little micro climate.