I've not tried it, but one of Samba 4's goals is to be able to create an AD compatible domain controller, so theoretically yes.
According to the Wiki, it already has (as of today - 25 Jul 2012):
- support of the 'Active Directory' logon and administration protocols, supporting XP, Windows7 and OS X clients
- support for Group Policy definitions
- full NTFS semantics for sharing backends
- Internal LDAP server, with AD semantics
- Internal Kerberos server, including PAC support
- Bind9 integration for AD DNS support (with DLS)
- fully asynchronous internals
- flexible process models
- new RPC infrastructure (PIDL)
- Python support - used extensively for client and management tools
- generic security subsystem (GENSEC)
(among a few others which I did not include as they were not functionally related).
The first bullet point should satisfy what you're looking for.
(Sounds like a good evening project, might just play with that tonight).