If they will do atm over oc-n, perhaps that would work better.
Ie, a perm virt circ for SS7 and as-needed vc’s for ulaw.
Atm oc-n cards with linux sw support are widely available, according to goog.
libss7 and and ast *might* need a bit of patching to work with it, but it shoudn’t take too much.
Sip/rtp over private ptp ethernet is an option with at least some of the ILECs.
They may call it virtual-pri or some such.
Of course, if they are installing an actual sonet ring, and not just a spur, that can have built-in redundancy, depedning on physical routing.