Eurodicautom's delegation just does not fit.

cf. the parties for whom I will not offer a trans. but they are to do with the incoming/outgoing debtor novation process:

délégant
délégué
délégataire

A lot of water has passed under the bridge since this question was asked, but it seems to me that 'délégation' here is notarial shorthand for a form of 'third-party payment', as can be seen in a number of examples here:

https://www.siv.archives-nationales.culture.gouv.fr/mm/media...

Let us not forget that the texts notaires churn out still are verbatim copies of what their forebears (often literally) produced as far back as the 1700s (link above).

In Droit Civil, a délégation is the "opération par laquelle une personne (le délégant) invite une autre personne (le délégué) à payer en son nom une dette à un tiers (le délégataire)". As several of the examples in the link above show, this operation is often performed with part of the proceeds from the sale of property, which is your case.

No power is granted to the creditors, but rather it is agreed that via the 'délégation' procedure, Party A (the seller of the house) agrees that Party B (the buyer) may pay Party C (a creditor of Party A) the debt owed by A in deduction of the selling price paid to A.

I rather doubt this procedure is followed these days.