New tasks are adddd to the backlog by any team or by area product owner who is getting the direction from the main product owner.
Regarding tracking our case is a bit special, because we are working as an external company, payed after closed task. In classical LeSS they shouldn‘t be strictly tracked, in our case our program manager is checking the status in the end of the sprint.
Communication is needed with other teams, it‘s usualy done by using chat tools and in ad-hoc personal meetings.
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