Red Hat is also strictly against copyright assignment agreements in general, and keeps many under the GPL, so few Red Hat projects could realistically be relicensed like this to begin with.
Aside from the fact that IBM had no involvement in the recent decision relating to git.centos.org (if I remember correctly, IBM found out about it when it was publicly announced), IBM has had basically zero influence on any aspect of Red Hat open source development or project or product licensing policy.
On the other hand, Red Hat has had some limited influence on IBM's open source practices. For example, IBM has moved away from using CLAs for its open source projects, I believe mainly out of a desire to follow Red Hat's example. I'm not aware of any use of copyright assignment by IBM projects.