Yes, you can do this. None of the callmanager specific items will be availible without extending the schema, though(like phone numbers, I believe).
Take the registry key referred to in this tech tip:
http://www.cisco.com/en/US/partner/products/sw/voicesw/ps556/products_tech_note09186a00800ab82d.shtml
Change the LDAPURL key to point to your netscape directory server port 389, change dirtype key to "Netscape"
There may be some security items that need to be adjusted, if you have issues, please open a TAC case.
