Managing users from multiple LDAP sources

In our environment, we have both eDir and AD with IDM synchronizing the users. All users exist in both trees. Some users have a homeDirectory on OES, while other have their homeDirectory on a Windows server. How can we import "both" sets of users such that users who have their homeDirectory on OES can have access to directories stored on Windows, as well as giving users who have their homeDirectory on Windows access to that and also to directories stored on OES to which they have rights?

TIA,
Mike