On el6 there is a patch to packstack to install the rdo release rpm on all hosts, not just the host that packstack was initiated form
(Note that is tied up with the if EPEL==y clause which is not strictly correct)

On Fedora though, there is no such code.

I'm thinking that this could be generic logic in upstream packstack.
I.E. simply, on all platforms:

    rdo_release=s.popen("rpm -q rdo-release --qf='%{name}-%{version}\n'")
    rdo_release=rdo_release[11:]
    if rdo_release:
      server.append("(rpm -q 'rdo-release' || yum install -y --nogpg http://rdo.fedorapeople.org/openstack/openstack-%s/rdo-release-%s.rpm ) || echo -n ''" % (rdo_release, rdo_release))