Makes sense and things are clearer thanks to your help.
The “insteon details” document you referenced is required reading (in my case re-reading!).
By creating a scene (this is fairly unintuitive) with ALL my devices as controller and EZSrve as responder I now seem to be able to get XML events…but only thru telnet to EZSRve…not via UI.
Only a forced/expensive refresh in ui will reflect device state. Is this a known bug?