Telecom Italia has separated the handover part from the FMC equation with its revamped UNICA offering what was re-launched in October 2007.
The new service is basically a Voice-over-WiFi offering for fixed Voice-over-Broadband customers. UNICA is therefore effectively a way to put on the same handset a mobile number and a fixed number. It is not a single number service as one would typically expect from an FMC offering. There is no handover involved between GSM and WiFi. So if you start the conversation with WiFi phone you initiate it using your VoBB number. When you move over to the GSM cloud you disconnect and redial using the mobile number.
Telecom Italia has nevertheless tested handovers successfully but does not see the need for it. One of the reasons highlighted is that the service provider needs to dynamically change the tariff during the handover and that has been a bit difficult to achieve. Another difficulty that I imagine is the requirement for tight integration with mobile operator network (in this case TIM) which is a major issue and UNICA in a way exemplifies the conundrum.
In terms of the service components, Telecom Italia has developed the softclient for the phone in-house. Most dual mode phones work but the service provider is mainly promoting Nokia E65. For the server component Telecom Italia uses Italtel. It is the same server that supports Telecom Italia’s VoBB service which serves over a million customers. Unica penetration has not been great. Out of more than a million VoBB subscribers, less than 10 thousand have so far signed up for Unica.