I feel your pain. well I would say convert to polys and do a level 1 smooth on it.. but you might have edits on subD that you could luse. I'm not sure how you have it right now. Although not the most thrilling option I figure your best bet is just to kill the tries buy hand. If you really want a MR render. A posibility would be for renders only to convert it back to poly with a high tensilation just befor render. MR will handel any poly's that are trie or N'gons.

I feel your pain, its a bummer MR will not handle them.