How much prep time does the monorail get?

I’m not sure how those two questions are related, but Batman’s very knowledgeable in pretty much all sciences, and extremely technologically talented, so I don’t see how he could not stop a runaway monorail.

I’m still trying to imagine how a ray can run…

Only if he could find an anchor of some sort.

No he’s not, and yes he could

If the plot demands it, then yes he can.