There are multiple ways to do that but I'm not sure I have enough detail here to answer your question.
I'll assume you use a Mitel 3300.
Are we talking about individual users or something like a main number that rings to an attendant?
Is the "Call Forward Always" a button you push to activate on the phone or is it a code?
It's entirely possible, that if a phone is ringing and a user can hear it, that the person can just pick up their handset and press a "pickup" button to answer any ringing call in the group.
I think you may have to provide some more details for a better answer.
Ralph