Yes: if you have mobile sim-card & voice-enabled 3G dongle.
No: if you want to connect to landline. In this case, you need other ATA like Linksys SPA/Obi110 to bridge landline and asterisk.
Asterisk gui login, click "System Info" first and "Call Features" afterwards, the RPi runs into the endless loop, "Waiting for XXX.XXX.XXX.XXX"(RPi's IP).
The asterisk -rvvvc shows:
== Parsing '/etc/asterisk/dongle_extensions.conf': Found
== Parsing '/etc/asterisk/extensions_macro.conf': Found