Sounds like you're trying to use the ESS feature with FM11/12 as a data source. That won't work (not supported).
You could use one of the supported data sources (mySQL probably easiest) as the go-between.
If, by 'go-between' you mean creating table(s) in mySQL to which both FM servers connect, that is our backup plan. We were hoping to avoid the middle-man.
If you don't have to dela with record locking issues, simply convert the shared tables to native MySQL and have both FM servers share the same live data: no middle-man