Not 3dcoat related but still on topic IMO.
:exports from rhino. obj, without chamfer and in Mudbox refine surface with subdivide selection:



also Tom Finnigan (tsplines founder) said
(I'm working on a T-Spline to SubD converter, which should work great with mudbox. It's still in an early state, but should be helpful.

I'm currently working on improving performance in 2.1, but I think I should be able to get it into 2.1 as well.

In the meantime, Juan's suggestion will work pretty well.)

http://www.tsplines.com/forum/viewtopic.php?f=9&t=29265