1. A method for system interoperability in communication networks, comprising: monitoring activity including a set of services currently being used by a mobile station within a first communication system; establishing context information related to the monitored activity of the mobile station within the first communication system, wherein said context information can be used in a second communication system but is incompatible with contexts within the first communication system; keeping said context information up to date; keeping said context information on hold while the mobile station is connected to the first communication system; periodically transmitting said on hold context information to the mobile station; and putting to use said context information when the mobile station switches to the second communication system, wherein said second communication system is not based on the same context as the first communication system.