There's an entire drama around Sony Ericsson and Windows Phone! Microsoft UK’s head of marketing, Oded Ran, indicated last September that there's a Sony Ericsson Windows Phone in the works. The company's own CEO confirmed an upcoming Windows Phone for this year, then came some more statements followed by a leaked image of a Sony Ericsson QWERTY slider Windows Phone prototype. Everything then seemed to disappear once Jan Uddenfeldt, Chief Technology Officer and head of Sony Ericsson Silicon Valley, said the company will not manufacture any Windows Phone-powered smartphone "if the operating system doesn't take off".
Again, while the two domains could be completely unrelated to Redmond's mobile platform, there might still be a (thin) chance that Sony Ericsson changed its mind, especially with all the goodies Mango brings. And, seeing the growing list of Windows Phone OEMs, Sony Ericsson might as well want to be part of the list and fun.