If the band is negated by another card (not the FBTN card, like Jacob banded to The Strong Angel) it is as if the BTN hero were never there, so it is not a BTN battle. So for example, Jacob bands to Captain, you block TFG, the result is Jacob vs. TFG in a non-FBTN battle.
If however the FBTN hero negates the band (like my earlier example of Jacob banded to The Strong Angel) then TSA negates the band and kicks himself out, and the remainder of the battle is FBTN.
