A network spanning heterogeneous call center system and method of operation is disclosed. A particular illustrative system is for use with a circuit-switched private branch exchange and a packet-switched private branch exchange. This system includes a circuit-switched private branch exchange interface, a packet-switched private branch exchange interface, and a processor. The circuit-switched private branch exchange interface is to communicate with the circuit-switched private branch exchange, and the packet-switched private branch exchange interface is to communicate with the packet-switched private branch exchange. The processor is coupled to the circuit-switched private branch exchange interface and to the packet-switched private branch exchange interface. A particular illustrative method of operation includes receiving a circuit-switched call event from a circuit-switched private branch exchange, receiving an internet protocol call event from a packet-switched private branch exchange, and processing the circuit-switched call event and the internet protocol call event using a call controller.