The GrantUnityAccess tool is for all versions of Windows - the reference to "NT" is really more generic there. All it's doing is making a mapping between your Windows account (or accounts) an a specific subscriber on the local Unity box such that they can gain access to the SA/AA for that subscriber without being tied directly to that user's NT account (or AD account as the case may be).
I assume you don't mean importing users here, by your description I assume you mean moving users between Unity servers in a dialing domain, right? Importing a user from AD wouldn't, of course, bring in their greetings and voice names and the like since they would not be there in the first place. If you're moving users between Unity servers then yes - all this is preserved - this is covered in the help file and the training videos available on it's home page here:
http://www.ciscounitytools.com/App_GSM4x.htm
No, there's no way to move call handler information between standing Unity servers a few at a time (DiRT, of course, includes all this info but it moves all data at once, not a few items at a time).
