Here's the mess: You hvae one set of digits coming into the Main DLC, its extensions matches those digits. The only way the other two are ringing is via the cover button. The cover button is also matching the digits coming in for the DLC. You can't make the same digits go to different extensions directly, and that's sort of what you seem to be wanting to do. As far as stripping and adding digits, it's an all or nothing sort of thing.
You may want to consider the use of a QCC with backup operators, but it has its own set of rules.
IF the operators are in the same vicinity, you could put in an analog device that would ring on an incoming call, and light a visible indicator, or ring a bell, then a "pickup bell" button on all the operator phones. This would work, but the cover button is neater.
Pepperz@newper.net