Whether participation is paid does not by itself decide the authorization question, and unpaid work is not automatically outside it. Separately, unpaid time carries real costs for the professional, so treat compensation and permission as two different conversations.
Negotiate compensation, verify permission separately
Ask the employer directly whether the pre-travel period is compensated, and if so from what date and through which entity, since payroll arrangements can carry tax and employment implications on the Canadian side as well. Then ask counsel about permissibility independently. An employer's willingness to pay is not evidence that an activity is authorized, and a refusal to pay does not make it safe.
Certain preparatory tasks, such as reviewing onboarding material or completing standard paperwork, are commonly treated differently from performing the substantive duties of the role, so ask counsel to identify precisely where that line falls for the specific tasks proposed rather than accepting a general assurance that preparatory work never counts. Keep a written record of exactly when substantive duties begin relative to the date status is granted, since a gap that looks small in an email thread can matter a great deal if the timeline is ever questioned later. Video calls, document review, or system access granted from outside the country raise the same permissibility question as being physically present, so location does not resolve the issue on its own.
Build in time, and budget for it, to get a clear answer before any task begins rather than after a schedule has already been set and travel booked.