National Grid Electricity Transmission plc — System Operation Northern Irland Ltd — Scottish & Southern Energy plc — SPTransmission plc B. Lista indicativa das entidades contratantes no domínio dos serviços ferroviários BÉLGICA — SNCB Holding / NMBS Holding — Société nationale des Chemins de fer belges/Nationale Maatschappij der Belgische Spoorwegen — Infrabel BULGÁRIA