OK, here is the theory - need more info on the customer problem to give deeper advice.
You want to get that data off of the Mac server and onto a NetApp platform so you can apply NetApp solutions. You can do this by file sharing (see the white paper) or SAN - or even both - depending on the data. For example, you could place a StoreVault at this remote site, connect it to the OSX server by mounting some NFS exports or mapping CIFS shares and moving all file sharing tasks over to the StoreVault. Then the StoreVault can replicate back to the FAS system as needed.
Application data in a Mac world is tougher because I do not know of a dependable iSCSI initiator for Mac. ATTO makes one that is qualified with NetApp but check with them to be sure all of the features work. There is also one that has been developed but is not supported by a firm called Studio Network Solutions - that one seems risky to me. I would not bother messing with Fibre Channel in a remote office for cost reasons.