One way around iCal's reticence re the selection would be to embed the Applescript in a Keyboard Maestro macro which was restricted to iCal and prefaced the script with a Cmd-C.
To quote Tom Lehrer, 'I have a modest example
here'
(This draft doesn't attempt to delete the items from iCal – best to test a bit before adding that – but Keyboard Maestro could handle that part too ...)