Shouldn't universities and other organisations plan for outages like this and prepare an alternative to Zoom for precisely these sorts of occurrences?
This isn't their area of expertise, and asking teachers to migrate to the backup and inform and assist their students to get online during an outage of unknown length isn't reasonable.
Snow days in 2020 will be replaced with Zoom Outage days.
(plus, training out of practise professors on two video conferencing systems? No way that would end well)