Is there a way to work on tasks across multiple tenants?

[Deleted]

Not sure if Planner is the answer.

I am looking for a way or tool that allows several people from different Office 365 tenants to work together on tasks.

Ideally that tool is part of the Office 365 family.

Yes, we could use Asana, but we think that a even better integrated tool (like Planner ;) ) would be nicer. 

So the ultimate question is: is there such a tool or way to do this?

Thanks for any pointer.

Daniel

[#2]

Planner is not the answer to this requirement due to the fact it does not provide guest access support yet. A possible alternative could be Project Online

[#3]

Juan is right..... But Microsoft has promised that Guest access to Planner will be available Q1 2018 as per their roadmap.

Microsoft Planner: Guest User Access
Microsoft Planner will support task assignment and collaboration with team members who are not a part of the tenant. This helps teams collaborate with their vendors and channel partners effectively.
Estimated Release: Q1 CY2018
Feature ID: 14702
Added to Roadmap: 06/08/2017
Last modified : 02/09/2018

[#4]

I hope you are right :) and they will be able to do it by the end of this Q, Let's see what happens :)