Tsukamoto said this was the fulfillment of a 20 years old dream, and that he could not be happier that this collaboration happened specifically with Tetsuo.
The producers spoke with Trent Reznor on the phone in January of last year, and Trent was eager to create the track. However, he did not send a song for a long time. When the Tetsuo camp heard about the Wave Goodbye shows, they had all but given up on this track. They continued editing for 7 or 8 months, and showing it at film festivals around the world, finally finishing the film on October 2009 -- without NIN song. But in February of 2010, Trent suddenly sent the song - and the song was, of course, fantastic! They were more than happy to redo the ending again and include the song! Because of that, the final version of TETSUO with NIN song is going to be shown in NYC for the first time.
Everyone involved felt like this was meant to be, and they're extremely excited.
Regarding the MTV Japan spot we posted earlier -- apparently after Mr. Tsukamoto submitted the clip to MTV Japan, a producer at MTV overdubbed one of the MTV themes of the era, much to the dismay of the director. What you hear on the commercial is a bit of a mash-up. This made him all the more happy about collaborating with Trent anew, without anyone else getting their fingers in the pie.
Since you made it this far, here's the trailer:
So when can you get a copy of the soundtrack on CD? According to CDjapan (where you can pre-order the soundtrack), it will be available for purchase on May 26 in Japan, with 16 tracks (presumably by Chu Ishikawa) as well as Trent Reznor's theme for Tetsuo: The Bullet Man. This info is all subject to change, but CDJapan has always been very good with their info in the past.
Thanks again to Akemi Nakamura for hooking us up with all the info she's got on this!