> ...getting a BARTD car running...
That's not the hard/expensive part. A museum with people who can take a camera car hulk/shell and turn it back into a K-M locomotive (pending availability of some prime movers) can certainly figure out a way to get 1000VDC into the car from a generator cart of some kind and lay a couple thousand feet of rail alongside their regular track to make 3-rail (std & wide gauge) track for running the car back and forth in manual-override (25 mph max) mode for people to take pictures. But that's not much better than stuffed-and-mounted, and would still require construction of high platforms to accept riders since the cars have no provision for ground-level access by ordinary mortals. For a Bay Area or even Northern California museum it's not worth it when people can run down the street and ride the real thing (albeit not original cars) at full speed and with the full "experience."

For a museum with a collection where a representative original BART car (or even short train - I could see doing a 3-car with A's at each end and a B or C in the middle) would be a good fit, a static display with ramps so people could walk through would be fine. It doesn't need to actually run. Of course, you would need a way to power the a/c and lights, but that's not horribly difficult.

Running a LIRR car with an added-on trolley pole is about the same as tying on a generator cart. Not original, a kludge made necessary by conditions. I applaud them for going to the effort, and it probably makes their members and visitors (customers) happy which, after all, is the name of the game unless you have government or institutional funding. I should have been more precise. Are any museums actually running LIRR (or other 3rd-rail transit) equipment using 3rd rail power at the museum, offering rides to the public? Thought not.