the burden of proof is on the CBC as the one making the claim. Its not on Ford or Blair to offer up proof to refute the claim.
The only claim the CBC made is that they were contacted by sources at Police Services regarding 911 calls made by the mayor, that quoted what the mayor said.
And since it has been well established that the mayor did make the calls (the main problem), and that he did use inappropriate language on those calls (an additional problem), we can conclude that the CBC has adequately established the story and that there was a source.
As for what was said verbatim, it is up to those who have the proof to establish it. Since it seems that the CBC does not have a copy of those tapes, and the police appear to have their hands tied about publicly releasing them, but say the mayor holds the ability to have the tapes released, then the only way to "prove" what was said, lies within the hands of the mayor.
So...we have an un-named source within the police claiming the mayor said certain things, and a mayor saying he didn't say those certain things (with Blair "sorta" trying to defuse the situation).
So we have multiple un-named police sources vs a proven pathological lier....neither can claim they are above reproach.
The mayor is the only one who can prove what he is disputing, yet chooses not to do so. There's only one reason he would do that....he knows that whether he said "b*tches" or "I'm effing Rob Ford" or not, is irrelevant to the fact that it will make him look bad.