I guess since this live material came out on BMG, and since Lasker was involved with the RCA box, that it seems to me as if it could easily have fallen within the parameters of that project. Technically no, it didn't belong to RCA... although they evidently have some sort of rights to it now, and it does include a period that's covered by the box (1940-42).
Hey, you're sure right about the price--I thought this was an $11.99 item, but I see that it's a much more hefty list $19.99! Never mind... got mine as a premium for pledging to my local public radio station. It is turning up for $9 used, but not quite the bargain that I thought at first.