Well you made me look. Thank You.
I recently abandoned recording a Canadian song, going on the 1923 rule but after following your link and doing a little more searching, I discovered that I can actually go ahead with it.
I found the following at http://www.socan.ca/pdf/en/Copyright2006Brochure-En.pdf
"The time-line
Canada's Copyright Act generally grants copyright owners
protection and the right to economic payment for the life of
the last surviving creator of a work plus 50 years following the
end of the calendar year of his or her death. Canadian law
applies to all activity in Canada and to works created by
Canadian citizens anywhere in the world. By the same token,
other countries abide by their own copyright laws, and those
laws apply within their borders. Some countries, notably those
within the European Union and the U.S., grant copyright
protection for "life-plus-70" years.
In other words; If the last author has been dead for more than 50 years (Canadian Citizens' Works) then the works become public domain.