OK, I just flew a quick mission in the Su-25 and it worked perfectly all the way through.
Remember that you have to choose a LEAD aircraft for the triggers to be enabled. If you choose a PILOT aircraft, nothing will happen.
You can change from the lead after the mission has kicked off.
Edit: This is the one I am using:
DCS_1.5_TTI_(Northern_Region).miz (1.6 MB)