It is possible to connect an E1/T1 tie route eg DPNSS to a router and have the data network tunnel the link. If your not concerned with feature transparency across the legacy PABX network the options are even better. Use the VoIP facilities of the data network to act as a distributed transit/tandem voice switch. Use the PABX to insert site codes into the number sent to the Voip and the Voip network then switches to the desired site. In this way you dont need seperate routes between PABX’s AND you dont end up doing multiple voip conversions.
I’ve done it in a large network of dissimilar switches (not 200 sites but exactly same troubles and principles) with high success rate.
Fax me your email address and I’ll
send you my contact details if you want to discuss it more.
++61 8 8110 5100