Well, it *would* know in advance what the signal route would be in most cases, because the route would be the set of links which exist when the command is sent, not when it was received.  What RT would need to know at time of reception is the location at time of sending of the point source of the final link in the chain before the probe, and calculate from that. I'd note that only really works when all the links in the chain are, say, within the Kerbin SOI and communicating out to a probe long-d