I haven't joined the Zbrush forums but I probably should at this point.

There was a typo in my original post. The question should have been "Does anyone know a way to stop 4R2 from removing unused vertices on import?" Also, I was exporting from Daz Studio 3, not 4. I'll try it with Daz Studio 4 and see if it works.

Zbrush removing unused vertices isn't related to subdivisons, I think. 

Download my free stuff here: http://www.renderosity.com/homepage.php?page=2&userid=323368