The aim of this paper is to study the implications of the decision of the French regulator to join the FCR Cooperation, a common platform for cross-border procurement of primary reserve. Two aspects will be analyzed: 1) increase of social welfare by cross-border procurement and 2) implications for entry of new entrants like aggregators of Electric Vehicles. Joining the FCR Cooperation will impact negatively participation of aggregators and might not result to lower costs for procurement of reserve.