I'm not a Nova guy, but AFAIK el6-* branches were retired and replaced
by compound builds from f2* branches (f20 is Havana for fedora20,
fedora19, and el6; f21 is Icehouse for fedora20, el6, and el7; and
master for Juno for fedora-rawhide, fedora20, and el7).
For Fedoras, we build packages in Koji, and we use COPR for EL[67].
AFAIK there are no internal Red Hat repositories for RDO. Obviously, we
have internal repositories for RHOSP where we diverge a bit from
upstream releases.