It is the answer to your question - it states Apple requirements - which does not include W8-BEN.
Had you searched the iBookis Author discussion group - there are a great many threads dating back two years and all ask the same question and all get the same answewrs.
You can also get the asnwer you were looking for, if you look at the bottom link I included.
If you open iTunesConnect and check out the Contracts and Banking section - and you can fill in the sections, if you do you will also fined that England, Canada and Australia have additional requirements. Australia,s are required to hold an ABN ( Australian Business Number) and English/UK are required to supply an iBAN from their bank. ( it is with regard to Apple sending money US - UK its an anti money laundering thing and not sure which country implemented it) BUT as the Canadian requirement was not relevant to any of my applications.. I dont know what it is.
To expand on the W8-BEN - I have two online accounts with "print on demand" websites, Tee Shirts Mugs etc,.
Both accepted the W8-BEN from UK/Australia residents until about 6 months ago and sent out notices that we would need to supplpy an EIN.
The links and application process explain the tax situation and much depends on what - if any - Canada and USA have any reciprical agreememnts on their nationals having income from the countrie they are not nationals!
IF you were in a situation whereby Apple deducted 30% of your income in tax, you can includes the totals in your ( Canadian) annual tax return and should have your due amount reduced accordingly.
As with all things relevant to income taxes, any doubts should be discussed with your tax advisor.
Use the links provided or simply Google your questions and I am sure teh relevant Apple pagees will pop up.. also you can contact iBooks support and pose your questions.... they will add to your collection of links to plough through!
Have you checked any I and others have supplied to you?
My suggestion would be to simply apply to the US tax office for an EIN number and submit it with your account application.