Microsoft Cortana will interoperate with Google Alexa’s voice activated devices  by the start of 2018, as shared in following article:

https://www.nytimes.com/2017/08/30/technology/amazon-alexa-microsoft-cortana.html

SEATTLE — The crowded pack of voice-controlled digital assistants — Apple’s Siri, Google Assistant, Amazon’s Alexa and Microsoft’s Cortana — are good at numerous things. They can help people play music, set up calendar appointments and check the weather.

For the past year, the two companies have been coordinating behind the scenes to make Alexa and Cortana communicate with each other. The partnership, which the companies plan to announce early Wednesday, will allow people to summon Cortana using Alexa, and vice versa, by the end of the year.

It is unusual for big tech companies to cooperate on important new technologies that they want to stand out from the competition. Amazon, Apple, Microsoft, Google and nearly every other big tech company is pouring huge amounts of money into making digital assistants that are smarter and can do more, seeing them as a new way for people to interact naturally with devices and online services.

The Amazon-Microsoft partnership started in May 2016, when Mr. Bezos raised the idea with Mr. Nadella at Microsoft’s CEO Summit, an annual event for business leaders in the Seattle area. Mr. Nadella was receptive to the idea, so a short while later Mr. Bezos emailed a draft of a brief news release that described how their assistants would work together, both men said.

In a phone interview, Mr. Nadella compared digital assistants like Cortana and Alexa to competing web browsers that provide access to the same pools of online information. “The personality and expertise of each one will be such that if they interoperated, the user will get more out of it,” he said. “That resonated for me and for him, and then that’s what led to the teams working.”