OK, here's the thing I forgot to mention. Actually it isn't in the book that I referenced either. I think the call has to be transferred to make it work. A direct call into the mailbox doesn't seem to trigger it.
My subscriber that is using Unity to queue calls is 2116. I have his Busy Trigger set to '1'.
I then built a CallHandler 2222 and did the above settings on the CallHandler and set it to Ring Extension 2116. I placed an call 2116 and made it busy. Then I called into Unity and hit the CallHandler, either by dialing 2222 from the Opening Greeting or making it an option off a Subscriber mailbox and it said that the extension was on the phone, press 1 to hold,etc. It told me how long I had been holding and how many calls were in front of me. Prompts me every 30 seconds to see if I want to stay on hold or leave a message.
Here's a not so good 'feature' though. 1st person in queue gets blips of MOH from CallManager, 2nd person in queue gets good MOH from Unity(?). It's a different MOH so I have to assume it comes from Unity.
I tried this on Unity 4.05 and Unity 5.0 with UCM 6.1.3. I don't know it this would work for a Hunt Group or not. If I get bored I may try it.

If it does work, you could build a CallCenter without IPCC if you don't need statistics.
Hope this helps someone.