There is an import option when you create a Deduplication Folder, but there appear to be many limitations to using this option. I found this while doing my research:
http://www.symantec.com/business/support/index?page=content&id=TECH160832
This article has not been updated for 2014, but Symantec support assures me the limitations still exist. During my migration I'm going from Windows Server 2008 R2 (with Backup Exec 2012) to Windows Server 2012 R2 (with Backup Exec 2014). It seems to be that wanting to do this will be a very common scenario among customers. Like many customers I'm also doing virtualization. The Technote isn't very clear about where the Agent for VMware and Hyper-V can't be installed. It can't be installed on the media server (that may have Hyper-V role installed)? It can't be installed on any server that is backed up by Backup Exec?
In any case that again will be a very common scenario. We really need full support for deduplication folders if we're expected to use them. We're on 2014 now and this isn't version 1 of deduplication folders.