Implemented in 4.2:
http://github.com/jstanden/cerb4/commit/5323da1f2fa5dfc9862e17c201e5174f2493a890

Verified implemented in 4.2 dev build 907.

As suggested when you move a ticket into a watched group, a notification is now sent as if the incoming message had been routed into the Helpdesk.

Now the new "e-mail notifications" system changes the basic layout, but all you need to do to make sure you set the "incoming message" event along with your watched group. You can even watch all groups and any time a ticket is moved, a notification will be e-mailed out. To watch all groups, do not checkmark the "Ticket >> Group/Bucket" criteria.

Expect this to be part of the next 4.2 stable release.