[Asterisk-Users] Busy message

[Aaron J. Angel]

asterisk-users-admin at lists.digium.com wrote:
> Sorry, it's "${HANGUPCAUSE} Asterisk hangup cause" as
> documented in docs/README.variables.  The cause code listing
> can be found in include/asterisk/cause.h

As twisted points out: "Hangup cause is different than why it couldn't
create the channel."  If that's the case, why are BUSY and CONGESTION
defined?  Are busy and congestion states ever reached after a channel is
created?