Quoting an Amazon review:
"In 1992 RCA/BMG released the first 82 CD Toscanini Collection.
That is the template upon which the new Toscanini Collection was assembled.
In 1999 RCA/BMG issued twelve 2 CD sets of Toscanini in new, 20-bit transfers. Most people thought these were an improvement over the 16-bit transfers of 1992. *
In 2006 Toscanini's Philadelphia Orchestra recordings were issued in new transfers.
Finally in 2008 Sony Japan issued 15 CDs worth of transfers on Japanese JVC XRCDs [most of this material overlapped with the 1999 20-bit transfers]. JVC XRCDs are highly valued by collectors - I could never afford them.
If you're adding this up, approximately one third of the 1992 set was re-done in new and improved transfers.
Of course, in an ideal world, someone would have re-mastered the remaining 2/3 using the latest technology, but this is not an ideal world.
GOOD NEWS: Sony took the 1992 Collection as a template, and inserted the new and improved masterings onto the appropriate CDs. Can't complain about that."