Without debating the utility of resuscitative thoracotomy in this situation, the question at hand is how long do you continue CPR?
This case-control record review concludes: no,15 minutes is insufficient.
Their review included 396 patients treated in the prehospital arena for traumatic cardiac arrest, almost half blunt injury, only 2.2% penetrating and the rest, inexplicably, of unknown mechanism. Hangings, electrocution, fires, decapitation and those already in rigor mortis were excluded.
Of these patients, only 4.8% of patients survived for 24 hours, 2.3% survived to discharge, and 0.8% achieved any sort of functional neurological outcome. Most of the patients who achieved these outcomes received longer than 15 minutes CPR: ROSC (21 out of 27), survival to 24 hours (16 out of 19), to discharge (4 out of 6), or had a decent outcome (2 out of 3).
So, if you provide CPR for longer than 15 minutes prehospital for traumatic cardiac arrest (largely blunt), then you might improve their chances of survival (let alone with good neurological outcome) from practically zero to almost zero.
What this study does not answer, though, is how long is enough, and when should resuscitation be stopped.