Microsoft and Nokia's industry-altering announcement of a strategic alliance back in February has today been bolstered with the signing of a definitive agreement between the two companies. In announcing the inking of the paperwork, the Microkia crew point out that they're already hard at work developing "a portfolio" of Nokia Windows Phone devices, which will be shipping "in volume" in 2012, but there's still a twinkling hope that they can get something out on the market in 2011. Nokia devs have started porting key applications and services to Windows Phone, with mapping and navigation getting a highlight mention, while there will indeed be a "Nokia-branded global application store that leverages the Windows Marketplace infrastructure." Notably, this is described as a single portal where devs can serve their apps to users of Windows Phone, Symbian and Series 40 devices -- it'll be interesting to see how they work out the details of that. There's also confirmation that Microsoft will pay Nokia multiple billions of dollars as part of the agreement, some of which will be spent on completing an intellectual property-sharing agreement between the two teams. So yes, the third ecosystem is well and truly on its way.