Far enough to complete the internal documentation, which is usually the slow part, and to absorb a request for further evidence, which is common in these petitions. Work backwards from the installation dates the subsidiary has committed to, and do not promise a customer a commissioning date that depends on an undecided petition.
Do not sell a date you cannot control
The pressure in these cases comes from customers. A subsidiary that has sold three installations for the autumn will want the technician in August, and the temptation is to file quickly with thin evidence. The better order is to build the documentation while the machines are still being manufactured, file as soon as it is sound, and tell the customers what the company actually knows about timing. Consider what can be done from Canada in the meantime: remote configuration, factory acceptance testing before shipment, and training the subsidiary's own staff in Ontario are all real options that reduce the dependency. If the timeline still does not work, it is better to move an installation than to place someone in the United States doing work they are not authorized to perform.
Hypothetical example: a robotic-palletizing calibration expert is scheduled for a U.S. factory launch before the company can retrieve a full year of foreign payroll from its payroll provider. A first review obtains the payroll dates first, then checks that the job description, client project plan and knowledge evidence all use the same timeline. The foreign-employment year is a threshold fact; a launch date cannot substitute for it. If the file is not ready, revise the project staffing plan rather than sending the employee to perform productive work before authorization.