As long as one end of the fax transaction is being conducted with an Asterisk based system, I’d say the net result is the same and that article applies.
Faxing over IP is a pretty miserable experience and I would never recommend it to any one who needs faxing for a mission critical application.
Having said that, there are a lot of things you can do to improve the experience, but it’s still never going to be 100%. Depending on your needs, that may be something you can live with or not.
In my own experience, I’ve had the best results with Digium and Rhino analog and digital cards using POTS/PRI. Again, not perfect, but for my application, good enough.
Results when using an IP trunk vary wildly. Some providers do a better job than others of building and managing a network that is more conducive to faxing.
I have personally had excellent results with Bandwidth.com and Covad (both of these use the Level3 network for what its worth) and less than stellar results with teliax and telasip (two providers who otherwise have excellent service and whom I recommend highly)
Plenty of high quality, low latency, short hop bandwidth is crucial if using IP trunks. A lot of horsepower in your system, like RAM and CPU couldn’t hurt.
There are whispers of better fax support coming in Asterisk …search the mailing lists and forums if you can wait until that functionality shows up.