Hi all.
So, just as an update, our vendor states Mitel has a solution called Twinning. I know how to set that up now, HOWEVER it's not how the old system was setup.
On the old system, you'd simply activate call forwarding in the phone settings of the phones (5330 and 5330e) and then when someone called your DID or ext (regardless if an internal or external call origin), it would ring the forwarded line, and then dump back to internal voice mail.  This was with call forwarding all, same as I am trying now (the other call forward options yield the same behavior).
Now, I've been comparing the current CoS to the old system's CoS, settings, etc, and for the life of me, cannot figure out how in the world that would have worked before. Currently, the forwarded line picks up for voicemail, which would make sense since the call would get handed off to them.  
So, let me ask...how would that have been controlled, as the old system wasn't configured with hotdesking what soever.  Twinning is too advanced to roll out right now for folks, so we want to stick to basics.
Seems like it should be a timer, but for the life of me, nothing I've tried works.  Here are the current timer settings though for the CoS for our phone CoS (the ones the users are told by the mitel system to use):
Call Forwarding/Rerouting
		Call Forward - Delay	0
		Call Forward No Answer Timer	22
		Call Forward Override	No
		Call Forwarding (External Destination)	Yes
		Call Forwarding (Internal Destination)	Yes
		Call Forwarding Accept	Yes
		Call Reroute after CFFM to Busy Destination	Yes
		Call Forwarding Reminder Ring (CFFM and CFIAH only)	No
		Disable Call Reroute Chaining On Diversion	No
		Follow Reroute on Disabled Forwarding	No
		Group Call Forward Follow Me Accept	Yes
		Group Call Forward Follow Me Allow	Yes
		Third Party Call Forward Follow Me Accept	Yes
		Third Party Call Forward Follow Me Allow	Yes
		Use Held Party Device for Call Re-routing	Yes
	Call Hold Timer	180
Ringing
		Delay Ring Timer	10
		No Answer Recall Timer	30
		Ringing Line Select	Yes
		Ringing Timer	180
On the old system, No Answer Recall timer was set to 125, and call forward no answer timer was set to 13. I tried those settings and it still didn't work.
It's almost like the old system shouldn't have done what it did and the new system 'fixed' it.
It would be nice to know where this all needs to be applied and what needs to be applied as from what I can see it SHOULD work, but doesn't.
Does this need to also be somewhere on the CoS for PRI, and or IP trunks?