"All Other Traffic" BT, once created, cannot be removed.
However, existence of this BT does not mean traffic will automatically flow in to this BT as you had alluded to in your original post.
There are only two reasons you will see traffic get caught by the "All Other Traffic" BT; If either or both of following are in place or occurring:
You have Business Transaction Lockdown enabled.
You have BT overflow situation, either at the Controller Application level or Agent/Tier level.
So if neither of the above case is true, you will see traffic get registered against any of your other "first-class" business transactions as you normally would. If there was load in All Other Traffic BT perviously, you will start to see the data fall off as new data no longer gets caught by this BT.
I know that presence of this All Other Traffic bucket BT does not make the BT screen pristine, however, these BTs do not count towards the limit, and the filter checkbox of Transactions with Performance Data will not display this BT (along with any other BTs) if there was no load present for them within the time frame you selected.
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