File as soon as the specialized-knowledge evidence and the corporate records are complete, and consider premium processing if the season is close. Do not send the specialist to begin the implementation on visitor status while waiting.
Evidence readiness sets the filing date
The petition can be filed once the company has assembled the process documentation, the employment records proving the year abroad and the affiliate's corporate and financial records. That assembly is what usually takes the longest, so start it well before any seasonal deadline. Once filed, the timeline depends on USCIS processing, which premium processing can shorten for an additional fee. A Canadian citizen is then admitted at a port of entry with the approval notice rather than through a consular appointment. Remote preparation can happen meanwhile: the specialist may configure systems from Canada and hold planning calls with the affiliate. What she should not do is travel to the U.S. terminal as a business visitor and begin the hands-on implementation, because performing the role before the status exists is the kind of fact that surfaces in a later extension request.
Hypothetical example: a medical-device sterilization company wants its Canadian validation specialist in a U.S. facility before a new line opens. The first review should verify the full qualifying year abroad, confirm the related-company evidence and gather the proprietary-process records before selecting a launch date. The employee cannot perform the U.S. role until the petition is approved and admission occurs. If equipment testing must begin sooner, the affiliate should use staff already permitted to work there. A five-year L-1B ceiling, minus any earlier L time, is the outer boundary for the schedule; it is not extended by project delay.