Multi Site Question

Hey everyone, I have a question on possibility and stability. Is possible for, and would the system be stable if I ran an * box at each of our 4 locations? What I want to do is set it up so that if some one in location A is trying to contact a customer from location B’s area then the call will be routed from location A to location B’s * box and made as a local call from there. We are currently on a S2SVPN Mesh with full T1 circuits for internet access. I do not currently have an * box running with the appropriate hardware, but once this occurs I am not sure what kind of local access lines to setup. Our main location makes the majority of the calls (about 25 lines in use at any given time) but 50% of them are to the areas where we have other locations. Those other locations generaly have about 2 - 3 lines in use at any given time. I have planned on potentially having a PRI at the main site for calls to areas where we dont have a location. Anyone have any suggestions on lines?