It's rare because the aircraft usually doesn't fly that high; in fact, it may require a light load (like they had, with no passengers) to get that high while maintaining safety. They still had to get permission to get up there, probably from a different controller; when they got handed off to the controller in Kansas City he commented on the fact that he rarely saw commercial jets at FL410. Trust me, if he didn't have permission to be at that altitude, the controller's comments would have been far sterner.
I don't know. It sure looked like they were on their own until questioned by KC controllers.