You can only move users between servers one at a time using GSM if they are in the same forrest - or you can move them all at once using DiRT. But there's no mechanism to get all user's settings one at a time between disconnected "island" boxes.
You can use Subscriber Information Dump to get a CSV dump of user data and get _some_ information over using the Bulk Import tool on the receiving side, but this doesn't get nearly everything (i.e. no contact rules, no greeting rules, no passwords) - it'll only get high level information like first/last names, extensions, billing ID etc...
