It seems obvious, but can I find it?
We have 1 trunk, and multiple aliases. Where do we set that the extensions present one of the alias numbers for their outgoing CLI?
Simon.

It seems to be directly attributed to the HUNTGROUP that the extension is in. Which isn't an obvious way of configuring it?
So it seems that each incoming trunk alias needs to go to a huntgroup with the individual extension in it.
Unless somebody knows a better way.