P&P had an expert and he said it could be anyone, because there's no way you can tie down who's on that one computer just using an IP address.
In fact, they've only connected a gateway IP address that might serve hundreds of computers to someone accessing a gmail account. There could be more than one person with access to the email account and the one who visited the website that the Ottawa Citizen set up isn't necessarily the same one who tweeted. A lot of the tweets look scripted -- as if they were set up to post automatically at regular intervals from an unattended machine.
They really don't have much of anything at all.