Sue the university on the grounds that this was a reasonably foreseeable event with proven solutions, i.e. properly proctored, in-person testing. "We're too cheap to do it" isn't an excuse.
I have done this competition (I think) and what your suggesting just is not reasonable. This is a distributed competition administered locally on a volunteer basis. This isn't some formalized test & trying to get Waterloo to pay for all the local proctors would result in this competition shutting down which would be net not good. I don't have insight into how the competition has changed in the 20 years since I took it so I don't know why they don't have local proctors or lost faith in them. Maybe COVID-era adaptations?
Honestly, I think the better solution is to adjust the difficulty to be AI-proof but it may be hard to do so at this level of academia.
Putting that aside, you don't just sue for money, you can sue for different outcomes and injunctive relief. For example you could sue to have the results released as planned.
Injunctive relief for not publishing known to be incorrect test rankings? Not likely.
A FOI request might get you access to the rankings if you really cared... I'm not quite sure what the contours of FIPPA (roughly equivalent to America's FOIA) is with regards to our universities but I believe it generally applies to them. At the same time it could easily fall within privacy limitations.