I have to question those stats. For one, it shows that YTV ranks higher in older-age groups (#10 in 18-34 but #5 in 18-49), gaining about 17,000 viewers between the ages of 35-49. This increase in viewership would most likely be due to children's viewership being attributed to the parents, rather than 30somethings suddenly gaining interest in SpongeBob and iCarly.
Second, TSN and Sportsnet rank in #1 and #2 across the board, which are predominantly viewed by men. This suggests a probable male bias in the viewership stats. CP24 Ontario is also listed in the "top 10" for 18-34, suggesting an Ontario bias rather than more representative national statistics.
Regardless, YTV remains one of Canada's most popular stations for children's programming, even if it does show Nickelodeon almost exclusively.