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Currently there is a very fundamental change happening in spectrum regulation, possibly the most fundamental ever in its history. This is the enabling of spectrum sharing, where primary (licensed) users of the spectrum, are forced to allow sharing with secondary users, who use license-exempt equipment. Such sharing is free for the secondary users, subject to the condition that they do not cause harmful interference to the primary users. The first instance of such sharing is occurring with the UHF digital TV spectrum, in what is commonly called TV white space. Regulators such as the FCC in the United States and Ofcom in the United Kingdom have indicated that other spectrum will follow suit. Cognitive radio is an enabling technology that allows such sharing. Following recent rulings by FCC and Ofcom and the emergence of a series of related industry standards, CR operation in TVWS is moving from the research domain towards implementation and commercialization, with use-cases that are of interest to telecom operators. In this article we describe three such use cases: future home networks, coverage of the street from inside buildings, and broadband access to rural and underserved premises. We present results of modeling and trials of technical feasibility, undertaken by the Innovate and Design team at BT. Based on our experience we draw conclusions regarding the feasibility and commercial importance of these use cases, and identify some of the remaining technical and commercial challenges.