That has only happened during a few HHN years. Only Universal TMs can access these pathways during normal operation.
It is extremely labor intensive to maintain the walkthru. It is technically possible because we do it for HHN, but it requires walking about a city block 'backstage'. There are a number of liability issues involved including crossing a functioning backstage street, a functioning studio production area and numerous hazards from set pieces, staff privacy issues, production crew privacy... it ain't a-happenin!