Again, i did our move months ago and i cant recall completely. But i think the calendar issue was caused by permissions. Our 2003 users could not sync their calendars at all until they were moved to the 2007 server. We tryed many things to resolve it and even RIM told us that because 2007 was still unsupported at the time that they couldn't help us beyond the normal troubleshooting. They were very helpful but the next step would had envolved their programmers/engineers which were alredy working on supporting 2007. So our solution was to just move them to the new servers.

edit: i just re read your post and i realized i was thinking you were talking about BB syncs. We have not moved to Office 07 yet so unfortunetly i have no information there :(