[arbuge]

It makes sense there would be some kind of immunity. "Immunity" is probably the wrong word - I'd call it common sense. I would think Google has a simple lookup table which always places results like "bmw.com" #1 for query "bmw", "wikipedia.org" #1 for query "wikipedia", etc. irrespective of backlink profiles.

[RBerenguel]

But there's no need to. Such big sources have huge anchor links with this tag, backlinks supporting them and whatnot. It should work organically without even needing a lookup table