As for the calling search space, one way I've heard it explained is to think of the calling search space as a key ring, and partitions as keys. If your calling search space contains a partition, you can access that partition. Remember that placement of partition within the calling search space also matters, as it is searched from top down. It appears you are running a very old version of CUCM. Is it really 4.x? Running on Windows on the Pub and Sub?

Justin