Sorry to say you are out of luck.
CA PPM only supports integration with one LDAP see eg
Does Ca Clarity PPM supports Multiple LDAP connection
Secondly that is an impasse.: CA PPM does not distinguish between users having the same user ID as the user ID has to be unique. Some people have used the full domain ID something similar to email address to solve that like
joe.smith@company_name.com , but out of the box the LDAP integration does not do that. I do not know if you can manually configure that.