Yes, there has been some topics regarding this on the forum.
The default way vicidial works is that it set the status to NA even though the carrier sends a "404 - Not found" for example
that's because in the united states you apparently cant trust the carriers, they might send you a 404 and a few minutes later the call could connect.
I researched this and found that you could look at the hangup cause codes in the database table vicidial_carrier_log
here is what the hangup cause codes means:
http://wiki.freeswitch.org/wiki/Hangup_causesThat's how you can differentiate them.
I wrote a patch that would set ADC to cause code 1 and ADCT (Auto Disconnect Temporary) to cause codes 19, 21, 34 and 38
This was added to the trunk 2012-11-29 (admin.php build: 121129-2319) disabled by default and its a system setting called "Enhanced Disconnect Logging" for enable/disable it