I've also searched the forum and found this from a post by Thorston, but as this is my first venture into this topic, I'm not understanding how to use it:
I've looked into the urban effect. This supports an implicit lightmap. The z-component of the normal map is read as emissive strength (well, the b-color channel) and the emissive color is declared in /Effects/urban.eff as <night-color type="vec3d">0.75 0.59 0.05</night-color>. So at night, if the urban effect is on, cities are illuminated with that color where the city normalmap /Textures.high/Terrain/city2-relief-light.png has a blue color value.
Which means that you can illuminate any urban/suburban texture you like by declaring a derived effect which inherits from urban and just changes the color value of the light, and then supplying a normal map which has no r and g color values but just specifies illumination via the b channel. This'd even work for roads I guess.
Any help will be much appreciated!