In the Oblivion E3 Videos wich you can download the TES site they say that it´s different kinds of Textures on each surface. On that picture they are using defuse-, specular-, parallax and normalmaps.

Lite-C Tut. 1 Lite-C Tut. 2 Lite-C Tut. 3 (en)
Shader Tutorial (ger)

http://www.slindev.com