Short answer: Nope, sorry.
However, I honestly have to question...
1) If this actually exists or not. It's only mentioned on Discogs, added by a user who has no other submissions and who promised to put up pictures of the cassette - but never did. Don't forget Discogs is like Wikipedia, anyone can add something, whether real or fake, and it will most likely never be checked properly.
I certainly haven't heard of any other French cassette libraries. By 1988 most were in the process of transferring from vinyl to CD, cassette wasn't a preferred format.
2) If it's indeed real, whether or not this is actually a library release. It doesn't have to be true just because this user says it is. Someone could have made a cassette of instrumental music in France under the name "Sigma 80", but that doesn't necessarily mean it's library music.
- A questionable, but interesting find