It looks like the desktop file is in the correct location - /usr/share/applications/, but I don't see it under System Tools or any of the other menus.
I've added the category 'System' to the desktop file in 0.4.11-1.
(Although it still doesn't seem to show up in menus. GNOME/KDE problems?)
I think you have to have Categories=Application;System;X-Red-Hat-Base; in your desktop file instead of Categories=System;X-Red-Hat-Base. It worked for me.
Fixed package is 0.4.12-1.
With redhat-config-printer-0.4.16-1, the menu item appears in the 'System Tools' menu for both KDE and GNOME.