From what I understand what your basically trying to do is take multiple textures/pictures and put them on the same surface at the same time. And beside writing a shader that does something similar to taking a source picture and emulating itself on the surface this is impossible. I believe as of A7 this is true as well.
In short, yes its possible, with a shader written for it. Long answer no its not really possible by the engine alone (last time I checked), but if you put effort into it you can do it no prob. Before you look into designing your own shader however look around for something that does this already, since taking one texture and relaying it on a .hmp terrain model and using another as a detail map is a definite possibility that I have seen done several times. Hopefully someone else can direct you more specifically.
P.S. Your link doesn't look
P.S.S. If your looking for a more specific answer, I suggest you elaborate, it may be me, since its late right now, but it didn't make complete sense to me to what you were asking.
