"...Google, Amazon, Facebook and Microsoft make the pilgrimage to Canadian universities, such as the University Waterloo, to woo engineering students out of Canada to build their careers in the United States"

And why does this happen?  Perhaps it has something to do with the rewards, professional development, and remuneration offered by these US firms.  What too many of these Canadian tech companies want is a pool of cheap foreign labour.  They don't want to train interns, participate in the development of young Canadian talent, or pay them fairly when they are experienced.  

I also call BS on the big numbers thrown around in terms of the 'tech talent shortages'.  Most of these companies are just fishing for "Purple Squirrels" (Google it...) and using this as justification for looking abroad for cheap labour.