RTC Database
One answer
The ClearQuest Import wizard allows you to import ClearQuest records from a CQ user database into a Jazz project area as work items. If this is the functionality you are looking for, see http://publib.boulder.ibm.com/infocenter/rtc/v2r0m0/topic/com.ibm.team.connector.cq.doc/topics/t_using_cq_import_wizard.html for more information. Since this only imports records from one CQ user database to one Jazz project area, you would have to run it for each CQ user database.