My set arrived on Monday. Have listened to about five discs.
If anyone is interested, it appears that this set uses 11 XRCD24 masterings that appeared in Japan. I listened to one and it sounds pretty amazing. Here is a list:
http://www.hmv.co.jp/en/search/index.asp?keyword=toscanini+xrcd&site=&target=SEARCH&type=sr
Pictures at an Exhibition is one of them.
All the mastering info is noted in the comments/reviews on the Amazon UK site. The Japanese remasters are not the only upgrades from the original edition. About a third of the set is "newer".
FWIW, I think I started listening to some of this material in the '50s.
Whatever they are charging for the set now, I really only wanted to expand my collection by about 20 cds. The set was cheaper and I have a bunch of bonuses.