File as soon as the year-abroad requirement, the corporate evidence and the product documentation are ready, and consider premium processing if the season is fixed. Do not start US work before approval and admission; the season does not create an exception.
Work backwards from the first day she must be on site
Hypothetical example: growers expect systems live by late October, and the subsidiary wants the engineer in Oregon by mid-September. The company should count backwards: admission after approval, approval after USCIS processing, filing after the evidence is assembled. Premium processing, where available for the form, sets a maximum government processing time in exchange for an additional fee listed in the fee schedule, which makes the calendar predictable. The slower part is usually the evidence: writing the product description, extracting design records and reconciling the engineer's employment history takes weeks if the company starts from nothing. Once the petition is approved, the engineer, as a Canadian citizen, presents the approval at the port of entry and is admitted in L-1B status; she should not enter as a visitor in the interim to begin the work. If the season cannot wait, the honest answer is that the subsidiary must hire locally for the first year while the transfer proceeds properly.
Hypothetical example: a manufacturer of commercial mushroom-growing equipment needs its fermentation-control specialist in Nevada for a new installation season. The company should first calculate whether the employee completed one continuous qualifying year abroad with the related foreign business within the applicable three-year period. Time spent in the United States in lawful status for a qualifying related organization, and brief U.S. trips, does not count toward that year but does not interrupt it; those dates must be documented so the correct period can be applied. It should then ask whether the proposed stay fits the L-1B five-year ceiling, counting prior time in either L classification and documenting any recapturable time abroad. Payroll records, entry history and the corporate relationship documents resolve those timing questions before the employer pays for a rushed petition. A published go-live date cannot repair a missing qualifying year or extend the statutory cap.