I attempted to have one city in the corner of the region broadcast ControlNet and start a new city in a different corner using money from the first city. Both ControlNet and money gifts are wireless, so it made sense for them to work to any city in the region. This is apparently not the case; wireless transfers appear to be restricted in some unknown way based on whether the cities are "connected". I know other resources can't be gifted or shared without a road, rail, or water connection - which of these three connections means determines whether cities are connected by wireless?
There are three kinds of regional sharing.
Clustering: city plots in the region are clustered around a great work site such that each city has one and only one great work site. Each site (and its costs and benefits) are shared by the cities in that cluster.
Dirct Road connection: Gifts and requests for regional surplus require direct road connections. Gifts include: Money, Commodities and Service Vehicles. Regional Surplus includes: power, water and ControlNet.
Any transport connection: Commuting residential agents (workers, shoppers, students) can use direct roads, indirect roads, trains, boats and planes to commute.