Just as an experiment I put 'ash press release' into Google and up popped this::
'New report finds major benefits to the health of the nation from increasing tobacco taxes'
(Friday 05 March 2010)
I then cut 'n' pasted the text of the press release into churnalism.com and, voila, I could see how much of that press release was blindly regurgitated by The Mirror and the BBC. In the case of The Mirror, it was 63% cut and 78% paste.
One limitation of the website is that you have to put in the text of the press release to compare it to the news reports, not the other way round. This is a bit of a bugger since the original press releases are not always easy to trace. Another limitation is that its archive seems to be limited to national newspapers. A quick google search found that the press release above was churned out by plenty of other local and regional newspapers.
Perhaps these problems will be ironed out as time goes on with the assistance of its users. If you have a source of press releases, do let them know. In the mean time, it could still be a useful little toy when you want to see how much of what you read is reheated PR guff.