In the current quest for personalized and omnipresent healthcare required to address new emerging population health challenges, the localised legacy concept of healthcare information systems is no longer expressive enough to address the complex interrelationships of the increasingly diversified technical environment in which the clinical processes occur. Thus, traditionally healthcare information systems architecture considered only clinical information systems and healthcare facilities; however, as the Internet-of-Things vision becomes a reality, an exponential number of mobile devices, sensors, tags and other identifiable resources with communication and processing capabilities will need to be added to the big picture. In such complex circumstances, the concept of interoperability also needs to evolve from the original concept involving pre-committed information systems to the capability of each information system to autonomously sense, interpret, understand and act upon arbitrary messages received from potentially unknown senders. Therefore, in this paper we propose an evolved concept of interoperability as a property of a system, more suitable to tackle the modern context of ubiquitous healthcare information systems. After defining the new problems faced by healthcare and concise review of the ubiquitous computing in the domain, we elaborate on the enabling factors for interoperable information systems involved in pervasive healthcare. Subsequently we attempt to assess and exemplify the impact that a novel Interoperability as a Property (IaaP) paradigm would have on the healthcare information systems' landscape.