using a vpn, i was able to connect to my callcentric (the free acct mentioned above) via x-lite (following guide at
http://www.callcentric.com/support/device/counterpath/x-lite). i made the test call, but the bandwidth was so low, that i couldn't understand the broken up test call. i assume it worked.
disconnected vpn and x-lite failed to connect {problem at server (sip error 408)} to my callcentric account.
i'll look up PBXes now and try it.