At one point it says:
‘Eh’ was so uncommon in normal Canadian speech that Schweinberger wasn’t able to get a sample size large enough to analyse it properly, which is why he turned to Kiwis, who used it “substantially more”.
I can’t vouch for the comparative numbers (I have only one Kiwi friend that can serve as a sample, and she lives in Canada), but my experience of living in Toronto is that Canadians say eh an awful lot. Which makes me wonder where Schweinberger was looking. Also, the supposed origin in Maori is suspicious. If so, why do Canadians use it so much? Otherwise, the article looks pretty good.
And I learned a new word: pakeha.