So it looks as though the article has been edited to say the anonymisation and aggregation was carried out before being transferred to a third party, which craps on our discussion a bit.

However, to answer your question anyway - I don't believe you could justify the work as being in the public interest. I think it would be an extremely tenuous link and I think you'd be a fool to try and rely on something as flimsy as public interest if you're not a government body, or processing data on behalf of one.

I suppose I was taking a stab at understanding what their thinking was to see if anyone else could provide me with something which I had not considered.