If ACD music/announcements (XMU configured as RCSU ports)
are used, ACD only switches paths, connecting caller TSL with XMU TSL.
If no payload possible, there is no mechanism to use alternate path to
listen to these ports. The call is still in ACD queue and can be routed
anytime to any agent using CSTA_DEFLECT_CALL_REQUEST as described in
Note 1 above. As alternative to RCSU ports, Call Directors can be used
(see use case
Scenarios with Call Director (AMO SCSU) ports (analog device)).