I've never used that card before, so I do not think I can really help you that much.... can you setup a trunk with the port from the TN556 card? if so, then you can use udp/aar to route the call to it, (see my post in the thread mentioned earlier)
If not, and you can only setup as a station, then I am sorry, I don't know how you would pass the info to the fax server....