It’s probably pervasive in second and third tier research universities. It’s not pervasive in top-tier universities. Actually it’s probably not pervasive in either case, but it happens more in the former.
I just finished my PhD at a "top tier" university. Everyone plays the same exact tricks. My group all self-cited and our collaborators and back and forth.
So there's no such thing as "top tier" as far as the quality goes, there's only higher paid.