Not really
Today, it is not permitted to ride around the loop: passengers have to exit at City Hall, then see the 6 train go around the loop empty, emerging a minute later, ready to collect passengers again. In the mid ‘90s, plans to make the City Hall loop part of Transit Museum efforts were publicized but abandoned a few years later. Thus, only the train drivers and conductors get to see the beautiful abandoned platform that hasn’t changed much since construction.
Though people still do it.