As others have pointed out, the answer is money when it comes to these projects. When I was at the Pennsylvania Rail Museum years ago I asked an employee there if they had any plans in the future to do any kind of excursions with the engines they had on display as an offshoot of what the museum does, and from what I recall of the conversation there had been discussions about that over the years, but that the cost of doing it would make any gains for the museum in terms of attendance impractical. So basically it is as others have said, that the Penn rail museum will likely always be static display only.
I suspect operating engines are going to be limited to tourist railroads and the UP as long as that lasts, with maybe some other private projects like the T1 project continuing to restore some engines as well. The local rail museum near where I live has a steam engine on display, but even with the enthusiasm the people running it have, they as far as I know aren't going to try and restore it to operating capability for the excursions they run during the year (currently using one of the Alco units owned by the local shortline whose tracks they are located on), the engine was used to run excursions back in the 70's and early 80's but it likely would be just too expensive to bring it back to operation to current standards and then maintain it in operation (the restoration is expensive, but maintaining a steam engine also is pretty expensive from what I know as well).
