I need to convert a node system made in blender internal render to cycles but I can't find a node that would replace the "Lamp Data" node.
It is not currently possible to get the incoming light vectors for materials in Cycles with nodes. This would be a lot more complex than in BI, because of all the light bouncing around in the scene - I suspect(just a guess) this is the reason this data is not exposed via nodes. In Cycles it should only be possible to achieve these kinds of results with OSL that is not supported by GPU rendering so I don't know much about it. I suppose it would require a separate question as well if you were interested to pursue this further.
Recently texture coordinates for objects where added, so it's now possible to do a dot product like in your setup with an empty. Instead of the lamp data node, you use a texture coordinate and set the empty, then you normalize the vector with a vector math node and then do the dot product with the normals of your object. For the color you still have to rely on the light's color. You also have to parent a light to the empty