The concept of a smart city has been identified as important aspect for responding to the challenges of urbanization and convenience for citizens. The information communication technologies such as cloud computing, internet of things and Service-Oriented Architectures can be deployed as a vehicle for catalysing smart city innovations. Information and sensing technology utilisation and integration of the urban infrastructures and citizens in new means paves the way to important aspect such as energy efficiency, the enhanced quality of life and better systems-of-systems collaboration. Arrowhead project develops a technical framework, which enables the collaborative automation by networked embedded devices. Collaborative automation is enabled with Service-Oriented Architecture. This paper discusses the Arrowhead framework applied in the smart city domain. We present two Arrowhead compliant smart city systems and their integration for creating new and enhanced system behaviour. The paper discusses integration of street light and car heating systems in order to create better user comfort and energy savings. The work demonstrates that the Arrowhead Framework allows to create multi-vendor system of systems applicable in the smart city domain.