Unfortunately, the issue with the STIR/SHAKEN standards is that the carriers don't believe that this deadline will be met. If I'm not mistaken, representatives of Rogers, Bell and Telus appeared before a House committee to request an extension of the deadline. I think that it's necessary to be firm and to require implementation as quickly as possible.
Canada's telecommunications networks are outdated. They won't make it possible to fully implement the STIR/SHAKEN standards. However, I don't think that this constitutes a reason to not begin implementation in the fall. It's just necessary to make sure that the pressure from the telecommunications lobby doesn't push the government to extend the deadline to 2021, which I think would be a mistake.