The deal, for which talks began in July last year, is intended to reduce costs for both companies.
Since joining the market two years ago, low-cost French operator Iliad has been leading a price war in the French market.
European competition regulators have opposed further consolidation in the sectorin recent years, but appear to be open to network sharing as a way for operators to reduce costs.
The two operators will reportedly launch a new bidding process for their network equipment and rationalise their existing contracts.