Well, I just tried some of this stuff. I used a "btn-view" button to inspect the new buttons I made:
"off-bd-alm" shows as "Off-Board DS1 Alarm". (Even though my R8 Admin's Guide describes that button with no mention of DS1. Typical.) But works great, thanks CL!
"busy-ind" (Busy Indicator) works great with trunk-groups. I had no idea you could do that. (They are also handy for making quick test calls to our fax servers, which use DS1 tie-trunks.) Thanks Kris!
By the way, my R8 manual also describes a "ds1-alarm" button, even though this button doesn't seem to be available any more. Good Job Ex-Lucent Proofreaders! Baah!
The two buttons, "mj/mn-alrm" and "major-alrm", also look useful. I think I'll put them both on my 2nd phone. (Guess I'll need a spare 8434 just for all the buttons I want now.) Thanks Colby!
The Automatic Circuit Assurance (and "aca-halt" button) seems kind of complicated. I did notice that you must not only enable it on the first page of the system features, but also in each trunk-group screen. (On mine this is on page 2, "ACA Assignment? y"

. However, I'm not sure if ACA will actually alert you if a trunk or trunk group is down, unless it's in heavy use. I think it's more for spotting intermittent outages or locked trunks. Has anyone used this a lot?