  We analyze the benefits of network sharing between telecommunications
operators. Sharing is seen as one way to speed the roll out of expensive
technologies such as 5G since it allows the service providers to divide the
cost of providing ubiquitous coverage. Our theoretical analysis focuses on
scenarios with two service providers and compares the system dynamics when they
are competing with the dynamics when they are cooperating. We show that sharing
can be beneficial to a service provider even when it has the power to drive the
other service provider out of the market, a byproduct of a non-convex cost
function. A key element of this study is an analysis of the competitive
equilibria for both cooperative and non-cooperative 2-person games in the
presence of (non-convex) cost functions that involve a fixed cost component.
