This violates the basic tenens of Insteon architecture but it works, for now. Add the ControLinc to EZSrve. I had to select No when asked if the initial responder link should be created in the ControLinc when adding the device. Since the ControLinc has no responder function I assume that is why an attempt to write that link failed so I added the ControLinc without the attempt.
Used EZSrve Scenes Management to create a link from ControLinc button 1 (controller Unit 01) to EZSrve as responder. Then used the SHN Utility to delete the Controller Of record for button 1 pointing to EZSrve from the ControLinc. This leaves the Responder To link record in EZSrve. Not a good condition to create because EZSrve could recreate the Controller Of link record for button 1 during a SYNCH operation, but… Now EZSrve will receive the Group Broadcast OFF message for Group 255 (0xFF) when the All Off button is pressed. Used the SHN Utility to confirm that an XML message is generated when the All Off button is pressed.
Don’t like the solution because of the fragmented link. Keeping the ControLinc side of the link to EZSrve seems harmless. I’ve seen too many flaky solutions posted on various forums only to have them stop working or work differently than desired under some circumstance. Use at your own risk!