I managed to get uv mapping to get pseudo-randomly change on each object having the material. I've based the randomness on the Object Info random output, and get the uv to be rotated, shifted and flipped: this make it possible to have group of identical object to look different, like bricks and alike.
The problem is that my nodes affect the diffuse and the normal map, but seems to fail with the displacement map of the material, as depicted in the images. As you can see in the node setup, the same final uv mapping (purple) is connected to the diffuse (yellow), normals (green) and displacement (red) maps, but only the least seems to ignore the uv mapping alteration.
What is causing this behaviour?
EDIT 1 Ok, i found out that the problem is not caused by my uv-randomizing nodes: displacement material seems to take in count uv modification only for distinct object, not for instances like dupliverts or particles. I think this is due blender internal architecture, and it's not a big problem for me, since particles can be made distinct objects with the "Make duplicates real" command. It shure would be great if particles and dupliverts could be affected by the uv alteration for displacement.
I also made a test file but i can't find how to attach it to the question.