Ah yes the mia_material, there seems to be some support issues with that part. Assign a lambert or some other standard Maya shader to the surfaces first, then load the the surfaces into the switch as normal, after that you can plug the switch into the mia and keep going.

The triple switch can be used to control any given number of objects. The "triple" refers to the number of channels it handles, like xyz values or in the case of color, rgb values. For a reflectivity attribute, the single switch would be more suitable.