According to the XSDs in jbossesb-4.7\xml (for example jbossesb-1.2.0.xsd) the route-to tag is not allowed threre (or anywhere else).
The 'property' element extends 'xsd:anyType' and only mandates that a name attribute be present. The value is optional and there is no constraints on the content in any way. This allows custom actions to receive configuration properties.
XML Spy 4.4 is reporting "element route-to not defined in DTD/Schema". I thought that the problem was that route-to was not declared as a type but probably the version if XML Spy I am using is too old.