Multi-access and heterogeneous wireless communications are considered to be one of the key drivers in the Future Internet. By using existing technologies, the mobile users will be Always Best Connected (ABC) anytime and anywhere while having full access to new communication services. This paper proposes the system architecture of a connectivity platform designed to implement the ABC paradigm for passengers using public transportation busses. Moreover, the main specifications of entities composing the architecture and the interaction mechanisms between them are also discussed. The key of our approach is the intelligent usage of seamless handover and load balancing techniques between several wireless access technologies offered by multiple telecommunications operators. While keeping the entire mechanism transparent to the data carrier, the system uses efficiently the available resources, maintains service continuity and offers easy and fast deployment. Besides the architectural aspects, the paper discusses some Network State Information management related aspects, presents spotted security issues and proposes a 3G - WLAN vertical handover algorithm based on the functionalities offered by the presented architecture. The experimental evaluation of the proposed algorithm shows a significant increase of the attainable transfer rate compared to classical handover algorithms, better selection of target networks being possible.