My only guess is that if Regina is on strike today stuff piles up in Winnipeg and Calgary and all over for Regina. Regina may open tomorrow but they don't get through the backlog. And my guess is that nobody is working over time or doing anything extra to help. And no doubt things break down when things are backing up.
They are in an uphill battle. Very few of us depend on the mail to receive cheques, pay bills etc. A Xmas card from Granny may be delayed but most of us can live with that.