hi chris, while i have not tried a drobopro with drobo sync,
i have been able to successfully (many times) replicate data from one of my drobos to another drobo of mine, using a tool called SyncBack (one of several tools they have)
if you do a search on syncback on these forums, it will hopefully provide you with several threads regarding the details and some other posts from others.
essentially, i use it to mirror (99%) of my 1st drobo, onto my 2nd drobo, (i say 99% because on windows i excluded a few recyle bin/volume hidden system folders etc so as to just mirror the data)
but i have also used it in these kinds of situations:
from 4-slot gen1 to 4-slot gen2
from gen 2 (selective folders) to gen1
from computer to gen1
from computer to gen2
from computer to drobo-S
from volume 1 of drobo-S to volume 2 of same drobo-S
and from computer folder to computer folder.
(this was all semi-auto and local / directly attached, but i believe one of the syncback tools supports networks too)
see if it helps you, and maybe post a question to those guys as well, and if you get it (they have a free version too) just make sure you learn how to use it and test using copies of some files and folders before you actually automate anything.
and please feel free to post back here with how it goes