Morning all, late last night Jason Kenny, the Conservative Deputy house leader, issued a press release on our tapes, see here for texts. In short, the Conservatives have produced an audio expert, Mr. Ron Dash, who says that three of the 'clips' that he examined seem unaltered and the fourth is too poor in quality for him to form a judgement.
There will surely be a 'battle of credentials' going on today, probably unnecessarily. Surely the recordings (at least of the Murphy-Grewal conversation of May 18 or the Dosanjh-Murphy-Grewal conversation of May 17) are as close to original now as is technically possible. (For a theoretical discussion of what that means, see here.) But what he examined were not the recordings that the Conservatives released to the press on May 31--the ones that created all of the headlines. Presumably these tapes are the ones the Conservatives slipped into Grewal's site once the news broke that the May 31 tapes had obvious signs of editing. The Conservative Press release announcing this, scanned at Nealenews.com here--of June 2?--said only a few seconds were different. But the differences are substantial--see the slideshow.
There are a lot of outstanding questions about what may be called the 'chain of evidence'. But for discussion of the tapes and their contents, I think that we should assume at the very least that three of the four recordings should be regarded as 'authentic'.
[Update. I've deleted several earlier posts on this subject, since they probably engage in unnecessary speculation.]