It appears that the decision to go with Windows Phone is closely tied to ABB's use of Office365 on a Global Scale. naturally Windows Phone plays extremely well with the subscription based cloud service, and both documents, email, and calendar synchronisation at the enterprise level as well as the personal level have allowed for a smooth integration process.
Microsoft’s Chief Operating Officer Kevin Turner:
Strong internal communications are the lifeblood of a company’s success, and ABB’s decision as a global technology leader to deploy Office 365 and Yammer will help it realize its vision for empowering employees with new ways of working via enterprise social and the cloud. When you remove barriers to productivity and innovation and enable employees to collaborate and communicate even more freely and seamlessly across organizational and geographical boundaries, incredible things happen.
It might be another very small win compared to other platforms and manufacturers, but it's a win, and both Nokia and Microsoft are doing the right thing in getting the story out there and in the minds of IT departments and corporate buyers. A constant flow of 'company X has bought into Windows Phone' will create more buzz, and a better reception of the platform.
The Microsoft press release can be found here.