Can a publicly owned municipal Wi-Fi network be viable?

The Institute for Local Self Reliance (ILSR) has published a preliminary analysis entitled "Is Publicly Owned Information Infrastructure a Wise Public Investment for San Francisco" (PDF format) on the financial viability of a publicly owned citywide Wi-Fi network. Media Alliance asked ILSR to investigate the economics of publicly owned infrastructure, i.e. when will the city get a return on its investment, how much in revenue will the network make, etc.