A couple of years ago in VIE, I went to the Sacher shop on Kartnerstrasse (around the corner from the hotel entrance) and ordered one shipped to my mother in California. She told me later that it was fresh and not dry (I had been concerned about that).
About the tortes themselves - IIRC the Sacher has an apricot filling, does the Imperial's version (also offered at the Bristol, BTW) have a different filling?