I'm running 275/60 and they do ok. They rub a little on low psi driving on the street and taking low speed turns. But yes, they do fit. I'm running a Hoosier tire.
The 50 is aspect ratio, it is the height of the tire from rim to tread. 275 x .50 = 137.5 mm or roughly 5.36" from the rim to x 2 = 10.72 + rim diameter of 15= a total 25.72" total diameter. That being said i just posted about this and people say the nitto 275 is slightly narrower then the MT.