The problematics of the positioning system are very similar with the FS estimation system and the channel allocation system.
If You are interested, You might consider doing some reading on European Patent EP1252786

This is a method of automagically selecting channels for a mobile network. When a network frequency plan is designed using the method described the density of base stations can be increased to a level that it no more makes any sense to locate the cellular using any triangle method or similar. It is fully sufficient to tell the cell it is now connected to as the cells are so close to each other.

Further more, in cities like Hong Kong or New York the tall buildings have a layered coverage scheme. Usually they make use of very small coverage micro cells (indoor coverage). Same applies to big and crowded places like subways or football stadiums.