is there JRE 1.6 available in some public Maven repository we could proxy in our Nexus?
if not, can somebody please provide a hint on how to deploy JRE to a Maven reposi
Your requirement is somewhat valid use-case. But IMHO, putting it in to a maven-repo is not the way to do it.
Other applications, achieve this requirement by getting the executables directly from the provider. For an example build servers like Hudson/Jenkins need to download Java/Maven upon users selection and AFAIR Jenkins download them directly from the Oracle site. (Since oracle asks you to login before download they use SSO mechanism). A similar solution along those path would be suitable for you.
Even if you host your JRE in m2-repo there are certain security problems. JRE is a sensitive program. Even if you say that you have hosted the same JRE from oracle, I would rather download it from oracle.