Balance of land units

I would like know exactly what functions that the Diplomat and Spy can perform (other than movement, observe, and attack) in your version of this game. For instance, in other versions of Civ I have seen the Diplomat can 1) steal technology from other'sources cities, 2) convert other's cities to your own, 3) convert other's units to you own; each of these are accomplished for a certain amount of gold (different for each situation). Cost for taking a city by conversion has a cost based on the size of the city being taken.