ok, the approach above worked out after a couple of tries using actionListener (I was not changing the correct attribute).
1- it fires when the tab is selected
2-it grabs the managed bean through:
ManBean mb = (ManBean) context.getExternalContext().getSessionMap().get("manBean");
3- it modifies the managed bean which is the "value" in the extendedDataTable
4- important!: add a f:subview around each -ui:include- to avoid a "duplicate component ID" error!
Would you say there is a better approach for this?