My esteemed colleague behind me, Mr. Church, provided me the adaptation from Elections Canada from the last election.
Subsection 289(4) states:
Despite subsection (3), where more than 500 votes have been cast at an advance polling station, the returning officer may authorize the count of the votes cast at the advance poll to begin 2 hours before the close of the polling stations on polling day.
This amendment is consistent with Elections Canada's adaptation from the last election, in terms of the 500 number.