Passing to a new era, the era of Smart and Sustainable Cities (SSC), has been widely related with the development of 5G networks in a mass scale. It is not only a matter of academic research but moreover a matter of successful implementation in order to achieve wide usage from the public and sustainable revenues for the companies. While the concept and the applications of SSC is widening, the more important the role of 5G networks seem to be. Current paper investigates the transformation of a city to a smart and sustainable city (SSC) as an opportunity for facilitating the deployment of 5G via sharing of infrastructures and as a factor of increasing demand for services. 5G is presented as an end-to-end communication system enabling a smart interconnected city with new business models evolving a variety of partners. Also, the variety of the partners and the stakeholders are presented, and the role of regulation is indicated for the implementation of SSC and 5G projects.