It creates a business deadline, not immigration permission. Have the actual assignment and applicable process assessed before work begins.
Keep emergency expectations explicit
Identify where the applicant would work, who would direct the activity and which duties are proposed. Report substitutions or changes before relying on the original plan. Avoid treating an urgent request as evidence that all L-1B conditions are satisfied.
Build the timetable around the two facts that cannot be compressed: the qualifying year abroad, which either exists or does not, and the evidence gathering, which depends on people who hold records and have other work. Hypothetical example: a customer reports a production stoppage on a lens-edging line and asks for a specialist within the week; the business urgency shortens no immigration step, and starting work before the applicable process is complete creates a problem larger than the stoppage. If the person originally identified becomes unavailable and a colleague is substituted, that is a different applicant with a different knowledge history, and the analysis restarts rather than transfers.
Record any change in the worksite, the supervising entity or the duties as soon as it is proposed. Set a review point in the calendar rather than waiting for someone to notice a change. A short check a fortnight before the intended start date catches the substitutions, worksite moves and scope changes that otherwise surface at the worst time.