Not until he has completed one continuous year of employment with the Canadian company, counted within the three years before filing, and reduced by any periods working in the United States. Three more months of uninterrupted Lake Country service is the minimum; more if he has already spent days at the US facility.
The year is counted in the past, not promised in the future
The one-year rule is a rear-view mirror requirement: the petition is decided on service already completed. A Lake Country company that hires a manager specifically to run a US acquisition therefore has to hold him in Canada for a full year, and that year must be with an entity that qualifies, which the Lake Country company does if it will own the US subsidiary. Hypothetical example: the manager started on 1 January, the acquisition closes in September, and the board wants him in Washington by October; the earliest petition date is the following January, later if he has attended weeks of on-site integration meetings in the United States, because those days do not count and can break continuity.
His previous years with a competitor do not help, because the competitor is not related to the petitioner. An alternative sometimes raised is to hire a different, longer-serving manager for the transfer and keep the new hire for Canada; that is a business decision, but it is a lawful way to move the date.