First, I am sorry if this is not exactly what you want and you rather
look for some plugin for your content-generation library and see it as a
consumer who wants the automatic settlement of the transaction.

But if you look for faxing solutions with java, you have different ways
to take this, of which the following 3 might make sense to you:

1. small scale: when you have the ATI commands to fax, get your hands on
java comm api and write your code against the fax-modem peripheral cards
or buy packages like http://www.java4less.com/java_fax.htm

2. build a queued fax server: use http://alpha.greenie.net/mgetty/ on a
linux box and some scripts as a backend fax server for your system and
develop your software to feel the queue and monitor your server (JMX or
whatever communication model you want on your java  side but the
interface to the fax server will be rather easier with a file-based
interface (polling))

3. Full scale PBX box: run an installtion of http://www.asterisk.org/
with add-ons for faxing in place (this might be an over kill as it is
not only for fax: you might run your callcenter on it)

NOTE: Using JTAPI implmenetations (e.g. j323 engnine of IBM) seems
elegant but i am not aware of any current JTAPI implementation that
implements the fax part as well.

I think you are better off with 1 (or its alternatives), or 2 (or its
alternatives), based on the usecase you got. write back if you have
further questions.