i actually don't expect that the science would uphold the premise that being held in a jail increases the risk of contracting the disease if the alternative is living in a shelter. if anything, you're at least sitting in one place, so your access to random people is restricted.
rather, i would expect that they would have better access to health care inside of the facilities than outside of it, as canada's coverage for refugees is patchy and uneven (and, i think should be). some of these people may end up denied access to health care altogether, as soon as they end up released. but, anybody that is incarcerated in this country should (at least in theory) get proper health care on demand.
i don't tend to support deporting people, but i would argue that crossing borders illegally should result in a criminal record and a period of detention, because it is in fact a crime in this country to do so. it's a kind of compromise that i think addresses the issue properly - if you can find a way in, then you can stay, but you should have a criminal record for breaking the rules in doing so.
refugee applicants that wish to avoid criminal records should enter the country through official ports of entry, as is directed by international law. or, those would be the rules under my direction, anyways...
arguments to look the other way at illegal labour stand in solidarity with the middle class that benefits from the exploitation of refugee labour and not with the working class, which ends up harmed by it.
so, again - say what you will of this, but this isn't evidence-based. and, it will no doubt just increase strains on the social system, potentially making the problem worse in the shelters, where the chances of spread are likely far higher than they are in jails.
https://globalnews.ca/news/6861756/canada-releasing-immigration-detainees-coronavirus-covid-19/