Nokia's CEO Stephen Elop and Microsoft CEO Steve Ballmer
"Nokia will adopt Windows Phone as our primary smartphone strategy," Elop said. "We will help drive the future of the platform, and we will bring Windows Phone to extended price points, market segments and geographies."
Nokia will bring "leading mobile devices," along with mapping, advertising, and global online store capabilities to the partnership, Elop said. Microsoft will bring Windows Phone 7, with its Bing, Office and XBox capabilities.
Nokia had three options, Elop explained. Symbian seems to have been written off from the start. Nokia didn't feel it could reach a board enough range of price points quickly with MeeGo, and didn't feel it could differentiate enough if it became an Android house, Elop said. That left Windows Phone as Nokia's path forwards.
There's still a lot that's unclear about Nokia and Microsoft's relationship. For instance: Microsoft has a very defined "chassis" spec for Windows Phones so far, which prevents phone makers from differentiating very much. Microsoft also hasn't offered super-high-end or low-tier Windows Phone options. But that may change: Ballmer said a "lower-end chassis" is coming, and Elop said Nokia would help Microsoft "move aggressively down the price continuum."
"We have very clear plans that allow us to differentiate within the Windows Phone ecosystem," Elop said. "It's a unique relationship."
We've reached out to Microsoft partners Samsung, LG and HTC to see what they think, and we'll update this story when we hear back from them.
One casualty of the agreement will be Qt, Nokia's cross-platform development framework.
"To introduce Qt to Windows Phone would fragment that environment, which would be repeating our mistakes of the past. With that in mind, for Windows Phones we will use Microsoft's developer frameworks," Nokia spokeswoman Laurie Armstrong said.
Elop went into a little bit of detail as to what will happen to Symbian, the smartphone OS that Nokia re-absorbed recently, and to Meego, Nokia's OS project with Intel.
"We expect as we transition through to Windows Phone we'll ship 150 million or more Symbian devices in the months and indeed years to go, but it's a transition program ... We'll ask [the MeeGo] team to change their focus into an exploration of future platforms, future devces and future user experiences."
But MeeGo could still surface as an OS for future Nokia tablets, Elop hinted.
"The third pillar of our strategic investment is in future disruptions," he said. "We reserve the right to introduce tablets with future platforms."
The partnership may finally result in Nokia's return to the US smartphone market, where it's been largely absent for years.
"This gives us faster access to the US market with a contemporary offering," Elop said.
We're sure to hear more at the Mobile World Congress trade show, starting Sunday in Barcelona, where both Ballmer and Elop are speaking.