CIFS is supported for DLO storage, but it is used as CIFS storage - not OST storage.
DLO is independent product, and does not use OST plug-in on DLO environment.
# Please correct if I have wrong understanding...
You may review following technote for more information :
http://www.symantec.com/docs/HOWTO23679 (Configuring a remote Windows share or NAS device for DLO Storage Locations using non-administrator case)
Hope this helps.