During a strike, an essential service of the Government of Canada is a service necessary for the safety or security of the public, or a segment of the public, at any time. An essential service could include a(n):

service
facility, or
activity of the Government of Canada
When a service is identified as essential, it means there are reasonable grounds to believe that the safety or security of the public would be at risk if a work stoppage interrupted the duties of the public servants offering the service.