If I understand your question properly, you're trying to tie more than one Team Project to a single Enterprise project. I think the original thread you're referring to
here is still applicable, because as far as I know, there have been no changes made in that area.
Though I didn't notice any changes between the MSDN "Integration Pack" and the TFS 2012 "Extension" (notwithstanding bug fixes, etc.), there is one documented one as outline
here.
But, as far as a major functionality change of the nature you're hoping for, I'd guess that it's not there (yet).