Can customer take one of tasks during the planning meeting, which was already assigned to this team, and put it to another team? For example because a customer think that the other team will be faster in implementing it? Is it normal for some agile methodologies? If yes, could you, please, provide me with the source of this information(book or web link), because I do not know how to handle it, especially because of team spirit: such a thing can make people in team demotivated and also there can origin some tenses in between these two teams...
It is part of some agile methodology and what are the constraints to make this thing?