User CAL question

I currently have a 2k domain with plenty of user cal's, ts cal as well as exchange 5.5 cal.
We are going to have a major upgrade and when its done we will have 2k3 dc and exchange 2007. From my understanding all the 2k user cal or any cal related to the 2k dc can not be migrated in the 2k3 dc.
this includes user cal. Is this correct??
My main question is
In 2k user cal was not a major issue. In fact, I do not think there were any technical restriction only legal restriction when you used it.
I know what microsoft will say if I ask them about 2k3 dc.
Has anyone attempted this???
I have attempted to add random ts license and user cal. But when I troubleshoot I do not see any changes from the origanl number of users given.

Thanks