I am one of the managers of a computing system that has a very restrictive set of outbound firewall rules but that does allow access to https://bioconductor.org/. Recently, one of our users reported an error accessing URL https://bioconductor.org/packages/3.13/bioc/src/contrib/PACKAGES

Investigation showed that this URL was redirecting to URL https://mghp.osn.xsede.org/bir190004-bucket01/archive.bioconductor.org/packages/3.13/bioc/src/contrib/PACKAGES

Since https://mghp.osn.xsede.org/ is not in our set of allowed external sites, that explains the user's error. Although we were able to provide this user a workaround, I want to learn more about this in case a similar problem arises again.

Was the relocation from https://bioconductor.org/ to https://mghp.osn.xsede.org/ a one-off event that we simply should let go?

Alternatively, is site https://mghp.osn.xsede.org/ a standard relocation site for archived Bioconductor packages so that adding it to the set of allowable external sites (a lengthy process on our side) will be worthwhile for the benefit of other users?

Older Bioconductor releases are currently migrated to https://mghp.osn.xsede.org/ . At the present time, this will be the standard location for any release that is not the current Bioconductor release or devel versions.
Therefore, Adding it to the set of external sites would be greatly beneficial.