I've actually been in this situation.
I was front seat passenger, and my partner was driving us emergency mode to a motor vehicle accident, reported as multiple patients and serious injuries. (The reports ended up correct. They transported 8 patients with 2 critical.) We were on a 2 lane rural highway, and the 2 vehicles in front of us pulled to the right, and he went to pass them on the left. The vehicle in front then turned left in front of us.
We hit her at about 50 mph, driver side, just behind the driver. Drove her into a telephone pole. All 3 of us were restrained, and there was no airbag deployment.
It took us several minutes to get out, only because our doors were crinkled. The agency I was working for had a large coverage area, and our closest backups from in agency were 20 minutes away. The local volunteer ambulance and fire department were about 10 minutes away.
She was trapped. It was about a 45 minute extrication. The volunteer agency transported her, but we started care. Surprisingly, she had only minor injuries.
My partner and I both denied complaints, and our medical director cleared us on scene.
I can tell you that few things have shaken me as much as that incident. It was clearly her fault. Based on our DriveCam footage, the police ticketed her. But after I got my head clear, we rendered care. It was BLS (I was a paramedic on an ALS ambulance), but we provided care.
I think that you are MUCH safer providing care than ignoring the patient. Were the patient to have a negative outcome, you would be accused of standing there and not providing aid. That looks bad in the public eye, and terrible if you happen to be on the stand. I've testified half a dozen times, and it's no fun. I think it would be far more difficult to defend why you ignored a patient than why you helped one.
The outcome? All the bosses were there for the company. My partner was suspended, and I was reassigned to another crew. No one ever asked either one of us if we were OK, or needed anything, or wanted to go home. (I didn't want to.) I'm still a little bitter over our treatment.