LiveUser with CAS / LDAP

Dear all,

In my organization, we have been using two locally developed PHP / MySQL
applications beside Moodle, Koha and Bugzilla: all of them having their own
local authentication. Where possible, we have our custom scripts to sync up
the authentication information among these applications.

The two locally developed applications I referred above make use of
LiveUser package to implement authentication as well as permission
framework.

At this point, we need to implement Single Sign-On. We are considering CAS
and LDAP. I understand from google search that Moodle, Koha and Bugzilla
will work with CAS as well as LDAP. But I request your advice and guidance
on how to go about migrating our PHP / PEAR based applications to SSO.
Specifically, following questions are in our mind:

1. What will be a good architecture / combination to use - CAS / LDAP /
LiveUser based customized permission management.

2. Can LiveUser's authentication framework be used with CAS and / or LDAP?

Regards,
Stephanas