I recently received word that Discourse, of course, a textbook intended for graduate courses in discourse studies, has been published by John Benjamins. My supervisor Geert Jacobs was invited to contribute a chapter and he asked me to chip in, which I did. The result is a sampler of how press releases are written at PR agencies and how they are rewritten by journalists.
Jacobs, Geert and Van Hout, Tom (2009). Towards a process view of preformulation in press releases. In Jan Renkema (ed.), Discourse, of course. An overview of research in discourse studies. Amsterdam: John Benjamins.