This shows the flow of the call when it comes in running 1.6.2.0-rc2.

CallerID has been replaced with NXXNXXXXXX and IP was replaced with 1.1.1.1:

    -- Accepting UNAUTHENTICATED call from 1.1.1.1:
       > requested format = ulaw,
       > requested prefs = (ulaw),
       > actual format = ulaw,
       > host prefs = (ulaw),
       > priority = mine
    -- Executing [NXXNXXXXXX@did-incoming:1] Goto("IAX2/trunk-02-1675", "incoming,s,1") in new stack
    -- Goto (incoming,s,1)
    -- Executing [s@incoming:1] Answer("IAX2/trunk-02-1675", "") in new stack
    -- Executing [s@incoming:2] Wait("IAX2/trunk-02-1675", "1") in new stack
    -- Executing [s@incoming:3] Macro("IAX2/trunk-02-1675", "start-monitor,INCOMING,NXXNXXXXXX,s") in new stack
    -- Executing [s@macro-start-monitor:1] GotoIf("IAX2/trunk-02-1675", "0?end") in new stack
    -- Executing [s@macro-start-monitor:2] Set("IAX2/trunk-02-1675", "MONITOR_EXEC=/var/lib/asterisk/scripts/handle-monitor") in new stack
    -- Executing [s@macro-start-monitor:3] Set("IAX2/trunk-02-1675", "MONITOR_FILE=INCOMING-FROM-NXXNXXXXXX-TO-s-ID-1253881638.0") in new stack
    -- Executing [s@macro-start-monitor:4] Monitor("IAX2/trunk-02-1675", "wav,INCOMING-FROM-NXXNXXXXXX-TO-s-ID-1253881638.0,m") in new stack
  == Spawn extension (macro-start-monitor, s, 4) exited non-zero on 'IAX2/trunk-02-1675' in macro 'start-monitor'
  == Spawn extension (incoming, s, 9) exited non-zero on 'IAX2/trunk-02-1675'
    -- Hungup 'IAX2/trunk-02-1675'