There are two issues with the Cisco Webex Meetings installer that make it unsuitable for silent install:
1) It launches the app in the next to last line of the postflight script
2) The postflight script contains a call to the binary PTInstall (embedded in
./PTInstall/Contents/MacOS/ which will prompt the user to quit the Microsoft Outlook or iCal (not Calendar) apps if they're running.
If I comment out item #1 and repack the installer it works, but if I disable the call to PTInstall then the installer reports an error validating files. Before I go down the rabbit hole further I thought I'd ask if anyone has gone through this exercise before can can share their experience.