Comment 0 for bug 1155114

quote 1 "When the device event occurs, the Event Monitor launches the application associated with that device event. The application is launched with arguments of Event:event_name and Device:STI_device_friendly_name on the command line. "
source: http://msdn.microsoft.com/en-us/library/cc836562(v=vs.85).aspx

quote 2 "/copy /c Directly copy from scanner to printer, using settings provided or default settings
...
/printer "printer name" Specify the name of the printer between inverted commas. If not provided, the system default printer is used"
source: icopy "readme"

So when you press the scan button, icopy called with arguments "/ copy /stidevice:%1 /stievent:%2" overriding the settings in gui program (icopy.settings), because see quote 2. Parameter /printer "blabla" not applicable because see quote 1.

PS
WIN XP SP3
iCopy 1.6.0.211
Canon MF 3110 as scanner and Canon IP 3300 as desired printer, Aficio FX16 as defaul printer in system.
iCopy manually registered as stilimageapp, registry settings attached.