Syncing iPhone Contacts with an Exchange Server
I'm using Google sync, which works like an Exchange server, so my experience may not be 100% the same as with a full Exchange set up.

I had to import all of the contact to the server (I did this through the Apple contacts app on my Mac) then synchronised them from there. I deleted all of the contacts from my iPhone to prevent contacts being displayed twice. So in short I'm not sure that it is possible to synchronise that group at all.

FWIW I also disabled synchronising contacts with my Mac through iTunes, leaving Exchange to handle all the contact syncing.