As an update to this story, CIPO has provided further guidance as to how it will handle outgoing mail during the postal strike.

CIPO will assess outgoing correspondence on a daily basis and will send essential date-sensitive correspondence via courier.  Additionally, correspondence and other documents with respect to opposition proceedings will be sent either by courier or facsimile.  It appears that trademark owners or their agents may also arrange for a pick-up service by sending a written request to CIPO.