At the moment the best option for those who need a working modem seems to get a MDC card that works, like the Si3054, to replace the Conexant MDC.
Cf:
http://www.silabs.com/Support%20Documents/TechnicalDocs/si3054-18.pdf
http://www.futurel.bg/datasheets/2/3054_PB.pdf
Even them, it will be far from perfect, cf https://freemor.wordpress.com/2008/05/16/si3054-and-hardy-heron-the-saga-continues/
Anyway, if you want to get one, search for "Modem 3054" on ebay : you will find many ML3054. As per the specsheets, it needs revE or later to be compatible with the HDA-Intel "Azalia" interface. Basically, make sure the original computer it was pulled from used snd-intel-hda instead of snd-intel8x0m (ex: lenovo y510 is ok) and you should be good.
I'm waiting for such a card, I will let you know if the modem works, but everything indicates it should. The modem could then be indicated as "working", but it will require a blob (for slmodem compilation) so personally I don't think I'll use the modem functions, but someone might be interested.
Charles