I'd be very cautious about listing any Auctions until the current urine production contest is over.
But if you are using Fixed Price listings, you can pull them down with a couple of clicks and put them back down again just as quickly.
If CUPW does strike, they are likely to protect their members' incomes by going for rotating strikes of a few shifts or at most days. This will be disruptive, but manageable.
If CPO locks out the workers, the whole postal system shuts down until Parliament orders arbitration and reopening.