Not in the United States. He may not perform the U.S. work before the petition is approved and he is admitted in that status. Preparatory work performed from Canada is a different matter and should be described accurately.
Pending is not permitted
Hypothetical example: a Grand Bay-Westfield shop faces a mill customer whose shutdown window is fixed, and someone suggests the fabricator attend for two weeks as a visitor to get the first installation started while the petition is pending. That is the arrangement most likely to damage the case, because performing the hands-on commissioning work is exactly what the L-1B is being sought for, and doing it in another status contradicts the petition. What he can lawfully do from Canada is finish drawings, write the commissioning plan, brief the U.S.
team remotely and prepare training materials. If the shutdown cannot move, the realistic options are faster adjudication, sending a colleague who already holds status, or renegotiating the window. Building the schedule around an approval date, with slack for a request for evidence, avoids the pressure that produces bad decisions.