This is one of the larger publishers in Italy and it has its own ebook distribution platform. I'm assuming that those ebooks will find their way to the Kobo ebookstore, but the more important question is who will be selling the ebooks in Italy?
Kobo still hasn't launched in Italy, though they do own the URL kobobooks.it. So this deal might mean that Mondadori might also act as Kobo's local ebook partner as well as sell the Kobo Touch. That would put Mondadori in the same group as FNAC and Whitcoulls as well as Kobo's other partners around the world.
In fact, the press release says "Mondadori will bring Kobo eReaders to market in the fall and will provide a complete eReading experience", which pretty much guarantees that Mondadori will also be the ebookstore. It would make a lot of sense to combine the local retail partner with a successful local ebook retailer.
Update: I've now heard back from Mondadori. Yes, Mondadori will be running the local Kobo ebookstore. (Boy, was that not clear in the press release.)