Absolutely. You could setup **91+10 in your ARS as a route to the B site. Then using digit modification, strip the **. (This assumes that site B uses 9 as their dial out digit.) The Bonaire PBX will see the 9+digits and output it according to its own ARS.
I'd maybe also setup ARS Route Lists, that take advantage of the opposite sites trunks. For example, I'd set site A to have the ARS digit strings of 91XXX of site B's local area code. That way if anyone from site A dials what would be a local call from site B, it would go over the route, and potentially save money on LD charges.
Or at the very least setup the Route Lists to provide some form of trunk redundancy in case either sides trunks fails.