The two seem a good match: Cortana, with its Bing-driven search technology and Alexa, with its Amazon shopping prowess and a broad base of hardware and software, could be ideal for the voice-commander crowd. XAPPmedia has helped launch over 800 media properties on Alexa and Google Assistant and LOVE SPORT is the first we have seen worldwide to launch simultaneously on both platforms.
At Build, Microsoft CEO Satya Nadella stressed the values of a more open system, saying "We want to make it possible for our customers to get the most out of their personal digital assistants - not be bound to some walled garden". Details of the partnership were spelled out a bit more, but it's still in its early days as neither company was ready to announce a concrete release time.
Cortana on Alexa can be summoned by using the command, "Alexa, open Cortana". Shortly after Google's announcement, Amazon stated that Alexa works with over 12,000 devices, presumably to flex on Google. As examples, Megan Saunders, the General Manager for Cortana choose to check calendar and send email using Cortana via the speaker during the stage demo. Taylor then booked a ride through Uber to his destination. So he just used Alexa on a Windows 10 PC. There, Microsoft promised multi-sense, multi-device experiences. Or you could ask Cortana to open Alexa, and use Alexa on devices such as your PC. Microsoft Layout allows Windows Mixed Reality users in defining a virtual floor plan and moves 3D models around in a VR headset while previewing how a room should look and feel.