I came across these links through google:

http://www.cellular.co.za/gsm_data-how-data-is-sent.htm

http://navasgroup.com/attwireless/fax.htm

I dont know the authenticity of the info from these sites, but they look valid, and one can find other articles through google that discuss fax over gsm. I think it depends mainly on the phone's gsm capabilities, and I'm not sure if the N900 supports gsm fax capabilties. Is there anyone here that can confirm if the N900 does perhaps support gsm fax capabilities? (if so this would be fantastic).