Of course you could make calls phone to phone with the Ericsson boxes.
Those blue boxes have one of the best quality of sound that I found so far.
With two of the webswitch 100 you could call phone to phone.
if you get a g4 box, you could call from phone to a phone line and beyond.
Need: A gatekeeper or static i.P. address.
I was told that works like a champ with some free linux based gatekeeper