As soon as the ownership transfer is legally complete, reflected in the corporate records, and the American plant can be shown to be operating. No waiting period applies, but assembling the charts and payroll evidence generally takes several weeks, and USCIS processing follows.
Let the corporate record catch up before filing
The order runs: closing, updated share register, evidence, petition, decision, admission. Filing while the ledger still shows the former owner invites a request for evidence, so the first task after closing is for the corporate secretary to record the transfer and issue certificates. In parallel, the Canadian company gathers Delphine's employment history and charts while the American plant pulls payroll, invoices and its lease or deed.
A petition built this way can often be filed within a few weeks. Premium processing shortens the decision for an added fee. She should not begin directing the American plant before approval and admission in L-1 status; attending meetings as a visitor is a different question that deserves specific advice.
L-1A time is capped at seven years, and extensions must be filed before the current period expires.