Yes, I am aware of the old rule. I came to Canada in that era too!!Those girls only had on campus work permit not off campus. Now again those girls are back in Canada after deportation.
http://www.ctvnews.ca/mobile/canada/deported-nigerian-students-back-at-university-of-regina-1.1860383
Good to know that those two ladies are back. But according to the report, they had SOLID political back up. Also they took extreme step like taking refuge in a church for nearly one and half year!!! For us, the commoners, it would be far wiser to be extra careful not to exceed the limit. We don't have anybody to pull strings for us. Also, during PR application, they do mandatory check for this issue (as far as I have learnt). Again, small hours here and there would probably be ignored but not long stretch of illegal work.
But it would be good to know if someone had a longer history of overwork (like a month of over work or more) and still got PR/citizenship. That will definitely prove my assessment wrong. Getting study permit extension or PGWP won't make a difference because checking would be merely random.
Just my assessment though.