So far, I found out two solutions (with a little bit programming).
Connect to the Asterisk server IP port 5038 and listen to NEWCHANNEL events with an application.
May be also you can configure your ATA so that it send new calls to any port on the PC connected to the ATA. Then you have write a dummy application server behaving like a mini-Asterisk (looping for waiting new calls events).
I did not try it ; but, my programmer’s backgroud tell me that it works. For doing that kind of programmation you need to have knowledge a little bit TCP/IP SOCKET programming in any programming language.
If you read french, you can have more understanding of the solutions in my thread (in Asterisk France) : asterisk-france.net/showthread.php?t=7283