How can I hear the audio from my AB100 on a panel connected to a M+3 system

You can permanently hear the audio coming from a 4w port on a single station by adding a forced listen. Take for example, - an AB100 console connected to port 3 on the matrix, - an ICS102 station, connected to port 17.
To make a forced listen in PGM_WIN, go to Configure --> Local Advanced.
From the list on the left, select "station" and highlight the required station, in this case port 17.From the list on the right select "interfaces" look for port 3 and check the box under the "Forced Listen" column.
This will permanently route the audio from the AB100 to the ICS102 and because the AB100 has a talkback button, then the audio will only be heard when that talkback button is pushed.