Cool find! These Radio spots would be nice to capture, unfortunately my player is broken. :(
Never seen that artwork before, is that the cover art on the novel, erri_wan? I do have a nice scanned collection of THX 1138 Posters and Lobby Cards but only from the '71 release, I also have the Italian poster SilverWook linked to a few pages ago, pm me if you're interested.
Anyway, the film was definitely set in the 25th Century. That's how the studio wanted it, not George Lucas. That's how I understand it from several interviews and articles I've read, Lucas even says this in the small TV-documentary from '71 "George Lucas - Maker of Films", where a young and skinny Lucas is very bitter about the whole thing. I recommend you to see it, if you haven't. http://originaltrilogy.com/forum/topic.cfm/George-Lucas-Maker-of-Films-documentary/topic/10403/
According to IMDB, the film was released in November 1971 in France after it had premiered on Cannes in May that year, so it's possible it could have played in Italy around that time, maybe for a short time. I wonder if the beginning narration on this version is an Italian thing afterall, it seems odd that they wouldn't mention that in the DVD documentary when discussing the studio interference. They don't going into details though but it's a pretty big thing to not mention but everything is possible of course.
From the '04 DVD documentary - A Legacy of Filmmakers: The Early Years of American Zoetrope:
George Lucas - "I did have a bunch of meetings with executives where they wanted to...you know, take the end of the movie with the people on the parking lot, the little freaks running around in the back of the parking lot and put that ahead of the movie and doing the whole thing as a flashback." Lucas describes an studio executive saying, "What we need to do is put the freaks up front!" Matthew Robbins - "They wanted to re-orchestrate the movie to get some of the bizarre things in the very first reel" George Lucas - "Finally they cut 5 minutes out of it, it didn't make any sense."
Here's one of the things Lucas says about it in "Maker of Films" from '71:
"Walter Murch did most of the soundwork, montages, what have you. The one problem is, that's one of the things Warner Brothers altered considerably, it was much more abstract and much more musical. The film was designed as a kind of opera, you know kind of a musical sience fiction film. And the soundtrack was composed you know under purely musical concepts and they didn't quite understand that, they thought they all had to tell the story. So essentially the biggest change is that they have injected more story, what they thought was the story, that's the story of...they took out all of the humor and the happiness and people laughing and stuff because they didn't..." (the interviewer interrupts him) :(