As far as i know PRIs will not be able to route calls based on ANI and route it to the PSAP but I *think* there is a SIP service that ATT provides that does this. Else you might have to look at putting a small router with 1 or 2 analog lines just for 911 (and SRST if needed). A 2901V/K9 bundle with FXO ports should help you with this.
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