When the court is called upon to rule on the assignment of contracts mentioned in article L. 642-7, or to record the transfer of a security interest referred to in Article L. 642-12, the co-contractor(s) or the holder(s) of the security are summoned to the hearing, at least fifteen days before the date of the hearing, by registered letter with acknowledgement of receipt, by the court clerk on the instructions of the administrator, where one has been appointed, or of the liquidator.