Uf, I'm goin' crazy here.
It basily works, but there is a problem. I have attached a zip maya file to show you the problem.
In this file I was just experimenting this thing, since I had problem in my scene.
So, what I did is:
I made too polygonal plane. I made a lambert shader, and assing color map (lets name it texture 1) and bumb map. Then I assigned this labert shader to the first plane.
Then, using bland mode, I made 2 additional shaders, but the same as the first shader is (with the same color and bumb map), and bland into one shader.Then I assigned this shader to the second plane, It work ok, but compared to the first plane, when I render the scene, texture on the second plane is is a bit darker on some areas then on the original picture. The alpha map is not important here (the one that is used for blending), since I have 2 excatly the same shader. (In the other scene,for example, I blended 2 defrent texture into one using alpha map, but still even thought the area on the alpha map is completly black, the final texture is still a bid darker then it should be. )

So, why are texture darker then they should be when I use blend tool? Is there some settings I havne't noticed, but I should?
Tnx!