I was wondering about it for a long time, what I haven't experimented with is this part of every tile parameteres:
[NormalTextureMaterial] EffectShaderName=terTerrainEffect.fx DepthBufferCheck=TRUE DepthBufferWrite=TRUE RenderedInOrder=FALSE AlphaTestEnabled=FALSE CullMode=CLOCKWISE LightEnabled=TRUE SpecularEnabled=FALSE EmissiveEnabled=FALSE FogEnabled=TRUE AmbientColor=1.000000,1.000000,1.000000,1.000000 DiffuseColor=1.000000,1.000000,1.000000,1.000000 ZBufferOffset=0.000000 BlendOp=ONE NumTextureStages=1 TextureStage[01].TextureName= TextureStage[01].MipMap=TRUE TextureStage[01].FilterEnabled=TRUE TextureStage[01].StageColorOp=TEXTURE_MODULATE_DIFFUSE TextureStage[01].StageAlphaOp=NO_OP
as far as I know there are various unused (?) parameters for TextureStage[xx].StageColorOp= and TextureStage[xx].StageAlphaOp= like BUMP SPECULAR etc based on looking into the terrainengine.dll
but I never had balls to experiment with those, also previously I think there was also additional parameter for TextureStage name (pre NA maybe?) would have to check older installations