Can the <receive> tag in VXML receive events from a back end service (non-CCXML)? Use case would be a call that is queued and waiting for next steps. Instead of periodically looping through subdialog to check status curious if it can be programmed to wait for the status to be sent (event-driven)? If so, what is the format that the message needs to be sent as? I'm not seeing a lot of documentation for this.