I was quite surprised to find that the GeneralCaptureSettelment is triggered if an army commanded by a captain captures a city. I have been using this in a campaign script for many months now.
I have been making some tests and I can confirm this: Captains also triggers the GeneralCaptureSettelment event.
I have seen that EB script uses I_SettlementOwner. If someone from EB read this, you can save a lot of lines in your script if you change to GeneralCaptureSettelment.