I might just be crazy (If I am please let me know) but I have noticed in both of the UEFA Champions League games played today you see AR1 (It is an Assistant Referee so I am assuming that it is AR1 because of how quickly they make it there. AR1 is the assistant referee on the bench side of the field) heading into the tunnel before coaches and players do and do not meet in the middle of the field with the other officials and leave as a 'team'. Why is this?
After the match, the fourth official must submit a report to the appropriate authorities on any misconduct or other incident that occurred out of the view of the referee and the assistant referees. The fourth offi cial must advise the referee and his assistants of any report being made<
LAWS OF THE GAME 2014/2015 As stated above he is responsible to report any misconduct out of the view of the referee and assistant referees. It's happened more than once that some misconduct happens in the tunnel between players and/or coaching staff. It might be his task to supervise the tunnel after the game (and possibly(or probably) during halftime also.
As far a I read, it's not stated anywhere in this document explicitley, but it makes sense.