Good news, this feature is partially done. :)
Planner tasks can now be copied to other plans. To copy a task, click on the “…” menu on the task. From there, you can select a different plan to copy the task to.
An error occurred while saving the commentKirsten A commented
We also have some use cases where we have a common task for all teams and would like it to appear on each team's board by it will be managed by the general user. Please add this feature