No. They can know on the basis that the files are hosted for download but that the site operators have made no revenue payments or signed contracts with the publisher/distributor of the media in question. The UK does not have the same kind of common carrier provisions in Telco law that exist in the US.
I don't think that the parent post was talking about common-carrier provisions[1]. The point being that the police are stating something ("these files were stolen") as fact prior to the trial. The assumption being that these facts need to be proven at trial. The same reason that the accused is called the 'suspect' and not the 'criminal' in police press reports. I'm not sure that this quite equates to something like saying, "he's a drug dealer," prior to getting a drug dealing conviction, though.
[1] Actually, 'common carrier' only applies to phone companies in the US. You're thinking of the 'Safe Harbour' provisions that are part of the DMCA.
The point being that the police are stating something ("these files were stolen") as fact prior to the trial. The assumption being that these facts need to be proven at trial. The same reason that the accused is called the 'suspect' and not the 'criminal' in police press reports.
However the police does call the victim "the murdered guy" and the place the arsonist burned "the burned down building". Some things are a simple statement of fact.
Similarly, the presence of "pirated files" is not something that is that difficult to examine and state as a fact pre-trial. And the other side would only win a libel trial if they could prove that this is not the case, which, I guess, it is. Else, they would be punished and counter-sued for that attempt too.
Edit: downvote away, but I didn't write the law, I'm just telling you how it operates: http://en.wikipedia.org/wiki/Digital_Economy_Act_2010#Sectio... The government is considering alternatives: http://www.ipo.gov.uk/types/hargreaves.htm