Public European TV stations usually were very good with archiving their stuff so if the SRF (RTS) produced it, they very likely have the tapes somewhere in a vault. If they only got the tapes from the French promoters and aired them unedited then I guess the stuff is gone.
Re. Lasartesse: I remember that he went to some trainings and maybe shows promoted by the scene that Claudio Castagnoli came from. He talked there a bit about his attempts to run shows in the German-speaking (Germans would argue that this is not really German, as a guy living less than 2 km away from the Swiss border, I obviously have a different opinion ;-)) parts of Switzerland (covering about 2/3 of the Swiss population) and drawing poorly. His conclusion was that Switzerland was (at least at that time) just not the right place for wrestling.
Cagematch has some results for shows in Switzerland pre 1990. The 80ies stuff looks to be CWA-affiliated, there is a 78 card that has an Inoki vs. Lasartesse main event where I think David Mantell posted some clips of, the 60ies cards look to be Lasartesse-run shows filled with French talent, the 40ies and 50ies cards might actually have been run by promoters in Switzerland (maybe promoted by Paul Berger as he pops on most cards and is the only Swiss regular from what I can tell).
And on why only the French station in Switzerland had wrestling: that's probably just simple geographics. I guess back then it was already possible for most people in the French-speaking part of Switzerland to receive French TV and probably wrestling on those stations was popular enough that it got coverage in newspapers and someone got the idea to air wrestling themselves, buying tapes from French promoters. You did not have that for the German-speaking side. I don't think there was (apart from clips here and there) regular wrestling on German or Austrian TV (and considering geographics, it would have had been German TV) that could have swept over.