"Blastic Scene" is considered a
semi-official release, pretty much in the same way as "Sonic Death", "Hold That Tiger", "Live In Venlo, Holland" and "Live At The Continental Club" (just to name a few), and i would bet that's the reason why those aren't available on the utkonos server. Check this information at Chris Lawrence's mustang site for specific details regarding "Blastic Scene":
http://www.sonicyouth.com/mustang/cc/071493.html
http://www.sonicyouth.com/mustang/lp/boot2.html
The fact that
"Live At The Continental Club",
"Hold That Tiger" and
"Live In Venlo, Holland"can be purchased at the Sonic Youth webstore, kinda makes me think that it's possible that "Blastic Scene" could be offered as an official (digital) release at some point, meanwhile i suppose there must be a working download link somewhere if you run a Google search. I took a look at two of my hard drives, and wasn't able to find a copy, which really worries me and i should keep looking as it simply would be a sin to lack this recording in anyone's collection. Sadly, though, i currently lack the time to do a conscious and deep search. If you post a request i'm sure someone might be able to hook you up with a copy of the audio and maybe the DVD, too (which i don't have). Sorry, i'm not able to help any further this time around.