And in fact I would second his point at the end: that an independent data recovery team might still be able to pull lost data from the servers in question, and therefore one should be called in. That's because I suspect that were the contents of these emails to be made known they would tell us little more than what we have already discovered, which is that the OLP panicked towards the end of the last election campaign and blew a ton of money to save a couple of ridings they would have won anyway. In other words, there are no secrets hidden in them; what the Libs did was all done pretty much up front and in public.
Incidentally, the video also seems to clarify a point WK made a few days ago:
[Cavoukian] pays no heed to the fact that records of emails concerning government business were kept by officials, and/or the government server, for many months and ultimately deleted only by them...
What happened on the hard-drive of some Premier's aide is far less important to the ultimate fate of the emails than what happened on the governments' servers. Whether or not emails were deleted from personal PCs to keep in-boxes tidy (or to cover something up--who knows?) would have no bearing on whether they were kept or not on the servers they passed through. And archiving material on the servers is someone else's responsibility (not our hypothetical aide's); if there was any failure of diligence, that's where it would have occurred.