There is a "format" between nurbs and polygon called "Subdivission", in MAYA we use The "Subdiveission" and in Rhino we use "T-splines"
I creat a poly model in maya, and turn it to "subdivission", and then turn "subdivission" to nurbs,and then export the nurbs to IGES to MOI.. and I can make a boolean hole on it, cut ,make curves---
If MOI can turn poly to nurbs directly like this,not just a Wireframe, is so cool, isn't it?
That is something that I would like to explore in the future for MoI, but it will take quite a lot of work so I'm not sure when I will be able to do it, it may not be for some time yet.
Currently probably your best bet is to use the T-splines plug-in for Rhino to convert such things into NURBS, it can convert them and save to 3DM format which MoI is able to read in.