There being much discussion if not suspicion on the topic, I contacted the NYCTA Museum directly. Here is what they said:
Anything that would be loaned for the exhibit would include a loan agreement and would be insured. We would be happy to clearly outline the dates the objects would be needed, how they would be housed and displayed, what our security for the exhibit is, and the objects could be picked up and delivered via either our curatorial staff or professional art handlers. The exhibit will only last for one month so the time we would need the objects would be approximately 6 weeks.
We're not trying to "take back" any transit related objects. As far as we're concerned anything that fell into private hands is your property not ours. We would just be happy to include some great artifacts in the exhibit and then everything will go back to the person that loaned them.
The museum folks are interested enough that they are going to visit with me to look over what is in the "Archives" that they might want to use in thier exhibit.
For those who are interested, here is the contact info........
New York Transit Museum
130 Livingston Street Floor 10