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No, never did anything like that, but I just recently stayed onboard a downtown #6 as it left Brooklyn Bridge station to get a look at the abandoned City Hall station as the #6 used the loop track to get to the uptown platform at Brooklyn Bridge. I recommend this to tourists and locals alike. (Just make sure you do it on a train that's remaining in passenger service! The automated announcement on the train will say something like, "The next stop will be Brooklyn Bridge, on the uptown platform.")

Is this really allowed?

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.

Source?

Here's a link to a 2007 NY1 story which quotes an NYCT official as saying that it is permissible to ride the #6 train as it goes around the loop track. I don't know whether the policy has changed since then, but AFAIK, the automated train announcements referred to in the story have not changed.

http://www.ny1.com/Default.aspx?SecID=1000&ArID=67432

They stopped all visits and tours to the City Hall station in 1998 over terrorist fears of allowing people under City Hall. At the same time they banned anybody from riding the train under there, not really sure what the fears were.

The information from 2007 seems to have indicated that has changed and you can not ride the train under there again, so I'll totally stand corrected on that.

Much to my surprise, checking the MTA website, they are also allowing tours back into that station, with the last one in May

Saturday, May 30 Noon to 1 p.m. and 2 to 3 p.m
THE JEWEL IN THE CROWN: OLD CITY HALL STATION
Capacity is limited; book early: Adults $20; Children $10. No strollers. Valid current membership required. Become a member of the Museum and join these exclusive tours!

Travel back in time to the early days of the subway! The starting point of New York City's new IRT subway was a jewel of a station, with chandeliers, leaded skylights, a vaulted Guastavino ceiling, and decorative tile work. Opened in 1904, the station exemplified the spirit of the City Beautiful Movement. The New York Transit Museum tour is the only way to see this treasure.

I have friends who have been on the walking tour through the station and loved it.

Agree. Sometimes it costs nothing to make things more believable without having to give up any artistic license or even far-fetchedness. Makes for a much better movie. My favorite example of this nonsense basically ruining a movie was "A Beautiful Mind". If you ever read the book, the truth was much more compelling than the fictional garbage represented in the movie.

On the other hand, another far-fetched loony movie that was actually well-thought out enough that it could be "believable" was "21". Completely contrived idea, but all the elements such that it could be true in our existing reality were in place.

In this latest one, as they were driving all over town with the money, the basic question "why didn't they just fly the money by helicopter from the vault to the hijackers?" arose in my mind. It was very funny when Mayor Gandolfini asked why didn't they just fly it there, and when Denzel went out to ride the helicopter to deliver the money, somebody says "finally some sense here" or something like that.

Obviously! No way that ANYONE can hijack the #6 because we're packed in like sardines. I'm still laughing at the very notion of hijacking the #6! That's the biggest inconsistency there IMHO.