An observation I've made with regards to trunks and their displaying of usage.

It appears:

For SIP:
Inbound calls show the trunk usage right away, if even before the call has been answered.
Outbound calls don't show the trunk is in use until the call has been answered - this is misleading as the trunk is in use even when people are just listening to a ringback tone on an outgoing calls.

For custom trunks using chan dongle:
Inbound and outbound calls show active in the trunk section for both inbound and outbound as soon as the trunk is in use without the need for the channel to be 'answered'.

I'd really like to work out how I can have outbound SIP calls show up their usage even before the channel has been answered.