I agree it will take time for the legal challenges to go through the system. However, I could see an eventual class action lawsuit on the fees, which, if successful, could result in people getting some or all of the fees back. It would be years before a final decision though. And that could be part of the government's calculation - discourage travel now and pay for everyone's quarantine later (through class action lawsuits).
Could be. Again, most important, won't help anyone right now.
I think the fees will hold for the following basic reasons (based only on what we seem to know now):
1) Government is not directly setting the fees (it seems, and they seemed to be very careful to avoid saying so, only 'estimates.') It may cost enough to act as a deterrent, but it's not structured as a fine/punishment/deterrent.
2) Instead, government seems to be setting the specific measures required (quarantine for specified days, setting standards required for isolation of travellers from eg facility staff, medical testing, procedures for staff of these facilities, etc). In addition it did this after widespread news that 'self isolation' by travellers was not being fully respected and not successful at stopping the spread of covid. (Even if you disagree with that news or conclusion, the test is whether courts decide they should second-guess government - and they likely will not unless transparently false).
3) Those specific measures (three days, testing, known issues with reinfection, etc) do not seem
on the face of it to be arbitrary. Instead, they do seem to be at least related to what is known of infection rates, asymptomatic cases, info about covid spreading on airlines/airport travellers, etc.
4) Cost calculation seems to be based on what it will cost to meet the government-specified standards (that govt believes is needed), i.e. cost of provision and not 'just a whack of money.'
As I understand the constitutional framework, courts are / are expected to be extremely reluctant to 'second-guess' government as to what measures are required and reasonable esp in context of an emergency. Meaning, roughly:
a) Don't expect courts to decide the measures are 'overreach' or excessive or whatever adjective you wish to apply unless clearly and obviously arbitrary and unjustified. (And I don't think a challenge based on airport measures being more strict than domestic measures will work either - it's not
arbitrary and unjustified for the feds to do what is in their power to prevent new infections being introduced into Canada).
Instead, broadly, the government
does have the authority/responsbility to impose measures it believes necessary to protect the public. (Government can be
wrong about those measures, but that's a different test than 'arbitrary' - I mean, don't expect a challenge to be successful just by arguing that the measures are not needed unless
obviously and transparently false and arbitrary; arguing that 'only' x% of infections are due to travel is a bad argument that will fail.)
If government were to impose some unrelated measures (say, every traveller arriving must do 1000 push-ups and 1000 crunchies), there would be a good argument for arbitrariness.
b) If my interpretation above is correct, the costs imposed are not unrelated to the cost of provision, not structured as a fine or punishment, but driven by standards the government has decided to enforce for a public purpose. (Neither is the fact that there are a limited number of quarantine facilities necessarily an issue - as an analogy, people who sell meat
must get their meat processed at government-approved facilities built and operated acc to certain criteria - and at a fee)
Also note as a 'fairness' issue - it's not like government is just going out and charging everyone in Canada $2000 for living in the same city as an infected person. The fees are only applicable to people already travelling to/from abroad. Airport fees are not 'unfair' on the face of it, either. Government can and does decide what 'public safety' measures are required for airports and those costs (fees) are built in to cost of tickets and travel (in some places charged directly).
But again, not a lawyer, armchair analysis only, and much will depend on implementing legislation and regulations; notably, I don't know which specific existing laws/legal frameworks will need to be invoked and how they all fit together. (Some more narrow legal challenge eg didn't fully/properly follow procedures required under some public safety act might well have better chances)