Hi,
I donnot reallu understand you architecture.
Anymay, AAR is used for distant site where the voice call used to use the WAN link tp proceed call.
The issue with AAR is that it is not supervising the WAN link its only a way of congestion controlled. It means if you allow 4 simultaneous call on you wan the 5th will use AAR.
If you WAN link is going down the only way you can do to force AAR is to setup the location to distant to value 1.
Rgds