Systems and methods for switching among networks (e.g., heterogeneous) and inter-working between a source access system and a target access system, by implementing tunneling from the AT to the target access system via the source access system. An inter-system handoff control component can facilitate setting tunneling by the mobile unit to the target access and/or between the source access system and the target access system—wherein signaling/packeting associated with the target system can be transferred over the source system.