Is it possible for one RHEV-M server to authenticate with multiple LDAP/IPA domains?

It is possible to authenticate against multiple AD/IPA domains with both RHEV 2.2 or RHEV 3.0.

Utilizing multiple LDAP domains may indeed work, but this functionality is not officially supported by Red Hat since it has not been fully integrated. This may be supported in a future RHEV 3 minor release.