Interconnected first and second radio access technology (RAT) systems simultaneously communicate with mobile terminals each capable of operating in both the first and second RAT systems. A given mobile terminal is capable of detecting it is within range of an access point of the second RAT while the terminal is in communication with an access point of the first RAT. It exchanges registration signals (412, 414) with the access point of the second RAT and only then does it provide an identification signal (430) indicative of registration therein to the access point of the first RAT. There it is used in determining whether to handover the terminal to the second RAT. Using this approach, there is no need for a complex measurement reporting system and, as another benefit, mobile terminals without dual-RAT capabilities are relieved of unnecessary radio measurements.