Those groups that you mentioned are only accessible once you become a eG or an eGO of TF2.
The group allows you to access a whole new area of the forums that only admin can veiw and discuss what is happening in the division.
Overall, it allows the TF2 admins (advisors and DLs included) to discuss problems that may occur within the division and keep admins up to date on TF2 matters.
I hope this is correct answer because from reading up on the groups its what I understood it to be. Hopefully, a TF2 member who are part of these groups can further answer your question.
Cheers!