Short answer. You do. Article 174 provides that where the System recovers damages from the third party in excess of what was paid or allowed under this Title, the excess is delivered to the disabled employee or the persons entitled to it, after deducting the cost of the proceedings and the System's expenses.
What the law says
Where the System recovers from such third party damages in excess of those paid or allowed under this Title, such excess shall be delivered to the disabled employee or other persons entitled thereto, after deducting the cost of proceedings and expenses of the System.
Labor Code, Article 174 — Third-Party Liability And Subrogation. Read the full provision →
The System is reimbursed, not enriched
The closing sentence of Article 174 is short and unambiguous: Where the System recovers from such third party damages in excess of those paid or allowed under this Title, such excess shall be delivered to the disabled employee or other persons entitled thereto, after deducting the cost of proceedings and expenses of the System. The subrogation that lets the System pursue the party at fault runs only as far as its own outlay. Beyond that point the money is being recovered on account of a loss that was yours, and the article returns it to the person who suffered it.
Two deductions, and no others in the article
Before the balance is handed over, the article allows the cost of the proceedings and the expenses of the System to be taken out. That is fair enough: the recovery would not exist without the case, and someone had to fund it. What the provision does not do is authorise a share of the surplus as such. So if an excess arises, the sensible request is for a statement showing what was recovered, what benefits were paid to you, and what costs and expenses are being charged against the difference.
Who 'other persons entitled thereto' are
Where the worker survived, the excess goes to the disabled employee. Where the contingency was a death, the phrase reaches the dependents in whose place the System stood when it paid — the same people the article names at the start when it says the dependents are paid by the System. This is a point families should raise early, since a recovery may come long after the funeral, at a time when nobody is watching for it and the household has moved on to other troubles.
How to be in a position to claim it
An excess is easy to miss, because the proceedings against the third party are conducted by the System rather than by you. Keep a record of the benefits actually paid to you and the dates. Keep your contact details current with the System and with your employer, and put your interest in any surplus in writing at the time the claim is made rather than after. Ask to be told the outcome of any action taken against the party at fault; the article gives you a stake in it.