Rule G.9: There is a 5-point penalty if the first team interrupts a tossup with an incorrect response. A subsequent incorrect interrupt by the second team does not result in another penalty; only one 5-point penalty may occur per question. The second team may still earn 15 points with a sufficiently early signal. Players may earn 15 points on power tossups at any point in the game, including overtime.
What you described is completely possible. A team that leads by 50 points with one tossup left (assuming no pending protests) could still lose if they neg, and the other team vulture-powers, 30s the bonus, and wins in overtime.
Coach, Bergen County Academies (NJ); former player for BCA (2000-03) and WUSTL (2003-07)
HSQB forum mod, PACE member
Stat director for: NHBB '13, '14; NSC '13, '14; ACF '14; NASAT '11