Bug #1129557 affects tabbed too. The `tabbed-user' script currently does not pass its parameters to the respective `tabbed' binaries.
tabbed-0.6-4.fc20 has been submitted as an update for Fedora 20.
tabbed-0.6-4.fc20 has been pushed to the Fedora 20 stable repository. If problems still persist, please make note of it in this bug report.