I grew up in Brooklyn, and frequently rode 1970's-era Electric Railroaders Association fantrips on the subway in the pre-Museum days. I was interested in seeing what Railway Preservation Corp. was all about.

Curiously, I find that Guidestar.org* has only a very sparse 1997 Form 990EZ posted, along with a note that the nonprofit status was revoked for lack of filings over the past 3 years. So what is the status of the Museum fleet, and any ongoing maintenance of the cars?

*You can look up any nonprofit's Federal returns - particularly their Form 990's - on Guidestar.org, albeit with a year or two lag.

You do realize that a large number of NYC subway stations are not even slightly handicap accessible, and it is wildly impractical to ever make them so.

Public transit vehicles do not need to be handicap accessible. There is no requirement for that anywhere.

What is true, however, is that once a ROUTE is made handicap accessible (however that may happen), you cannot REMOVE access.
"Access" means a reasonably large percentage of runs are handicap accessible. You are certainly allowed to run some vehicles which are not accessible. They just can't be the majority, and they can't be in big clumps. Typically, you add such vehicles in as "trippers" during the commute, since those vehicles are part of your reserve fleet.

As an example, Muni hung trolley-bus wire on the 31 Balboa line in the 1990's. Prior to that, they had run diesel buses which had lifts. They only had one kind of trolley bus, it was near EOL and it did not have lifts. So they could not "switch the whole line to trolley". However they could and did run trolleys as trippers during commute hour.

The first new trolleybuses with lifts were gigantic articulated monsters, intended for the 14-mission and 30-stockton, insanely busy lines. Their first assignment was the 31 Balboa, where they were vast overkill. But they had lifts.