Sorry, clearly I have not been using the correct words after reading your last post. Create a controller link between the device you want to monitor and the EZSrve/EZBridge as a responder. With this you can trigger a macro from the device on/off action. Insteon devices do not send messages on the powerline unless they are linked to something. Without a link there is no message to monitor. You can press the SwitchLinc paddle On/Off and it will control whatever local load is connected to the SwitchLinc. However, the SwitchLinc does not send any message on the powerline unless the SwitchLinc is a Controller (contains a Controller of link record). This is not unique to a SwitchLinc. Motion Sensors, ICON switches, ToggleLincs, RemoteLincs, and on and on do not send Group messages (the method Insteon hardware devices communicate with each other) unless and until they have a Controller of link definition and responder devices do not react to the controller messages unless they have a Responder to link record. A Group message sequence is made up of two Insteon messages. The second message is directed to a specific responder device and that responder device address is contained in a Controller of link record. For every device that is to be notified of the SwitchLinc paddle press, a unique Controller of link record is required containing the Insteon address of the responder.
There is an Insteon Details document in the public domain section of the SmartLabs web site. Perhaps becoming familiar with the general Insteon architecture and the requirement to link Insteon devices together will help in understanding the requirements of Insteon hardware. The above has nothing to do with EZSrve or EZBridge. HouseLinc2 (Smarthomes PC based home automation software), PowerHome2 (another very popular PC based home automation software) have the same requirements. Insteon hardware devices send Group message sequences only to devices that have been linked as a responder.
X10 devices are assigned a House/Unit code and connected to the powerline. They blindly send those codes and any device that happens to receive it can react to it. Very easy and very unreliable because one never knows what device(s) if any has received the X10 messages. With Insteon, controllers and responders are linked together, allowing the responder device to ACK messages that are directed to it which also allows the controller to repeat a message for which no ACK is received. More complex to establish, more complex to administer, but has the capability to be extremely reliable. Hope this helps clarify Insteon hardware requirements.