Yes you can use hair models from Daz or Renderosity. It will require the model to be imported with 3DXchange (or 3DS Max) first.
A word of caution. Some hair models from Daz are high polygon, complex models which may impact on performance in iClone. I have found the simpler hair models work fine but it is a trial and error process so be aware that not every hair model will work well. If you scale and position the hair roughly in 3DXchange first, it will only require small adjustment in iClone to get a good fit.
Peter EdwardsForum Moderator
iClone Daily Blog