The interactive voice response (IVR) auto-attendant mechanism can support the handling of inbound calls on Foreign Exchange Office (FXO) ports and outbound calls on Foreign Exchange Station (FXS) ports, including analog phones configured through the POTS and Cisco IP phones configured through ephone-dn virtual FXS ports. "
ISDN/PRI means PRI. I agree it is not clear, but BRI is not supported.