A conference management system in a first telecommunications network comprising: a receiver that is configured to receive a second message from a second data-processing system specifying that a first conference is starting, wherein the first conference is identified by a first conference ID in the second message, wherein the first conference involves a predetermined set of entities identified in a first message (403, 407) transmitted to the second data-processing system; a transmitter that is configured to transmit: (i) the first message (403,407) to the second data-processing system, wherein the first message specifies a subscription to events that involve the predetermined set of entities, wherein the subscription causes the second data processing system to monitor for all events occurring for the first conference ID, and to transmit notifications to the conference management system when the events occur, (ii) upon receiving the second message, a third message to a third data-processing system in a second telecommunications network, wherein the third message specifies to the third data-processing system to monitor for activities related to the first conference and to notify the conference management system of the activities, and wherein the first and second telecommunications networks are managed by different service providers; and a processor that is configured to coordinate, based on a fourth message being received from the third data-processing system subsequent to the transmitting of the third message and that specifies the first conference, the establishing of a communications link between a first bridging device in the first telecommunications network and a second bridging device in the second telecommunications network, wherein the first and second bridging devices are being used by the first conference. a receiver that is configured to receive a second message from a second data-processing system specifying that a first conference is starting, wherein the first conference is identified by a first conference ID in the second message, wherein the first conference involves a predetermined set of entities identified in a first message (403, 407) transmitted to the second data-processing system; a transmitter that is configured to transmit: (i) the first message (403,407) to the second data-processing system, wherein the first message specifies a subscription to events that involve the predetermined set of entities, wherein the subscription causes the second data processing system to monitor for all events occurring for the first conference ID, and to transmit notifications to the conference management system when the events occur, (ii) upon receiving the second message, a third message to a third data-processing system in a second telecommunications network, wherein the third message specifies to the third data-processing system to monitor for activities related to the first conference and to notify the conference management system of the activities, and wherein the first and second telecommunications networks are managed by different service providers; and (i) the first message (403,407) to the second data-processing system, wherein the first message specifies a subscription to events that involve the predetermined set of entities, wherein the subscription causes the second data processing system to monitor for all events occurring for the first conference ID, and to transmit notifications to the conference management system when the events occur, (ii) upon receiving the second message, a third message to a third data-processing system in a second telecommunications network, wherein the third message specifies to the third data-processing system to monitor for activities related to the first conference and to notify the conference management system of the activities, and wherein the first and second telecommunications networks are managed by different service providers; and a processor that is configured to coordinate, based on a fourth message being received from the third data-processing system subsequent to the transmitting of the third message and that specifies the first conference, the establishing of a communications link between a first bridging device in the first telecommunications network and a second bridging device in the second telecommunications network, wherein the first and second bridging devices are being used by the first conference.