7. (1) Where an accident happens to a workman in the course of his employment under such circumstances as entitle him or his dependants to an action against some person other than his employer, such workman or his dependants, if entitled to compensation under this act, may, at their election, claim such compensation or bring such action.
(2) If an action is brought and less is recovered and collected than the amount of the compensation to which the workman or his dependants are entitled under this act, such workman or his dependants shall receive compensation for the difference.
(3) If the workman or his dependants elect to claim compensation under this act, the employer, if he is individually liable to pay it, or the Commission, if the compensation is payable out of the accident fund, as the case may be, shall be subrogated plenojure in the rights of the workman or his dependants and may, personally or in the name and stead of the workman or his dependants, institute legal action against the person responsible, and any sum so recovered by the Commission shall form part of the accident fund. The subrogation takes place by the mere making of the election and may be exercised to the full extent of the amount which the employer or the Commission may be called upon to pay as a result of the accident. Nevertheless, if as a result of this act, the employer or the Commission happen afterwards to be freed from the obligation of paying a part of the compensation so recovered, the sum not used shall be reimbursable within the month following the event which determines the cessation of the compensation.
Agreements or compromises effected between the parties respecting such action or right of action shall be null and void, unless approved and ratified by the Commission and the payment of the amount agreed upon or adjudged shall be made only in the manner indicated by the Commission.
(4) Notwithstanding any provision to the contrary, the Commission may exercise its recourse against a municipal or school corporation or the Conseil scolaire de l’île de Montréal, by reason of an accident to a workman, within the twelve months following the date of the receipt of the notice of election contemplated by subsections 1 and 5 of this section, provided that such notice of election be communicated by the Commission to the municipal or school corporation concerned or the Conseil scolaire de l’île de Montréal within the thirty days following the receipt thereof.
(5) The election as between the above recourses shall be made and notice of it shall be given in the manner provided by section 5.
(6) If the workman has the right to make the election mentioned in subsection 1 of this section, the Commission, in special and urgent cases, even when the workman has not elected or made a claim, may furnish such workman with the medical and surgical attendance his condition may require, and the expense thereof shall constitute a privileged claim ranking immediately after law costs, upon the amount of the judgment to be rendered, if action be afterwards brought.