In the post that awjr links to above the author claims that a Mojang employee has interpreted the previous EULA for them as allowing this ("I personally discussed our rank system with a member of your business team at Minecon last year and he confirmed we were in compliance with the EULA. The only rule was to not sell Mojang IP [...]"), although it does not make it clear as to how official their discussion was.
With my question I didn't mean to imply that I have an opinion on this matter either way. I'm mostly wondering if the big server networks could try to cut out Mojang based on their shared (I assume) interpretation of how to the EULA has changed over time, whether it be right or wrong.
Edit: clarified last sentence.