In case you haven't seen these already:
- http://support.ptc.com/WCMS/files/157363/en/WindchillVisualizationServicesGuideWC10-2_M030.pdf (page 361)
- http://www.ptc.com/cs/help/windchill_hc/wc102_hc/index.jspx?id=ConfigDistributeFileServerWork&action=show
- https://support.ptc.com/appserver/cs/view/solution.jsp?n=CS141668
- https://support.ptc.com/appserver/cs/view/solution.jsp?n=CS26028
I can say from experience that if you don't have a cad worker at the remote site, upon check-in the files will be copied across the WAN for publishing (directly to the cad worker), then copied across the WAN again later during replication.
Based on Patrick's comments above, it sounds like a product idea needs to be created for Windchill to choose the nearest cad worker (based on where the object is currently located) when publishing starts executing instead of at the time the queue entry was first created (ready).