Comment 17 for bug 849624

The way firefox (and thunderbird) handle commandline switches was changed, I think after fx1.0. Support for that was added to calendar after 0.2.x. So testing with older versions doesn't tell us much.
You need to look at calendarService.js for the code. Also, take a look at bug 378557, which also involves commandline stuff. Maybe that bug blocks this one.