I think they Astroturf a lot. At least on this site. Any thread about a class at Stanford/MIT/CMU (often because they posted the textbook for free) and someone from Waterloo will post what they teach, no matter if it's relevant.
It's also a giant school (36,000 undergrads and 6,000 postgrads) and from what alumni told me, undergrads are incentivized to apply everywhere and especially during the off-cycles (winter) for internships when they are effectively the only ones looking.
Contrast that with Stanford that's barely 7,000 undergrads and 10,000 grad students).
I think they also have to get internships to even stay in the program (it's coop) so I guess that weeds out the unemployable.