The embodiments herein relate to a method in a RAN node for determining which operator that should serve a device when it has been handed over from a source network to a target shared network. When the device has been handed over to the target shared network, the RAN node transmits, to a non-registered CN node in a non-registered domain, a request for an identity of the device. The RAN node transmits a request, to CN nodes in a registered domain, for a serving operator which has registered the device. The RAN node receives information indicating the serving operator. The RAN node determines that the same serving operator which served the identified device in the registered domain should also serve the device in the non-registered domain.