Their suspicions? Well, Disney's recent announcement (which I expect someone will eventually tie to the recurring speculation regarding Jobs becoming Disney's CEO) and the iPhone efforts - which, incidentally, have been going on for a year without any visible progress, especially if you consider that the most credible prototype/mockup photos haven't changed significantly since the first E398-based mockups (aside from a new music button).
Their evidence? Well, besides speculation from Rob Enderle, absolutely zero. And, what is most disturbing from a financial news source, there's not even an inkling at what might be a viable business model for Apple as an MVNO - they can't possibly be serious about iTunes on phones being a driver for them going mobile, and the article smacks of total unawareness of what an operator (yes, even an MVNO) has to focus on.
But I'm not at all worried about the lack of credible reasons for Apple going mobile - given the current standards (or utter lack thereof) of Internet journalism and Apple's rating as an eyeball magnet for just about any technology-related news, a veritable horde of pundits is sure to be revving up their weblog editors even as I type this.
Let the spin begin.