No. L-1B employment begins only after approval and admission in L-1 status. Short business visits for meetings are a different activity with their own limits and should not shade into doing the assignment early.
Meetings are not the assignment
Hypothetical example: a Quispamsis firm wants its analyst to attend a two-week kickoff at the U.S. affiliate before the petition is decided. Attending meetings, observing and consulting with colleagues can be permissible business-visitor activity, but writing code, integrating the model and training U.S.
staff is the productive work the L-1B petition exists to authorize. The firm should define the pre-approval visit narrowly, keep the analyst on Canadian payroll, and have him carry evidence of the pending petition and the visit's limited purpose. Once approved, he can be admitted in L-1 status at a port of entry as a Canadian citizen without a visa stamp.
Extensions should be filed well before the initial validity ends, and the five-year L-1B cap should be tracked from the first admission.