The simple yet unsatisfying answer is: No. It's not possible.The simple yet unsatisfying answer is: No. It's not possible.
(Verified by a Blender developer, I had the same question a while back)
Followup explanation:
It would be possible to implement such a feature if cycles would render a second pass, meaning that it would render a complete image with the base shader and then re-render everything on the basis of the result of the first pass. Both passes would have to be noise-free, so this would effectively double the render time for each such connection that you use. And that doesn't take into account that a ray may bounce back and forth several times between two objects, and in theory, you would have to compute a new image for every single bounce then, as the result of every bounce is influenced by the previous one and needs a full pre-computed first pass of it.
Doing this for the full depth of possible bounces is impossible. Doing it only for the first bounce is against the concept of Cycles as an engine that renders continuously instead of in steps or with pre-computing anything. After all, Cycles also has to work in realtime, and that would be impossible to implement because there, you can't wait for two noise-free passes to compute for a usable result.