A lot of European cars have really poor rear visibility. In fact I think someone once told me at the driving club that the DVLA won't let you take your test in the new style Mini due to having too poor a view through the rear window. Having the rear camera on might be very useful. I know some car interior mirrors show the rear camera view as an overlay. That'd be handy.
From a UK perspective here are our highway code rules for dealing with emergency vehicles
Rule 219
Emergency and Incident Support vehicles.
You should look and listen for ambulances, fire engines, police, doctors or other emergency vehicles using flashing blue, red or green lights and sirens or flashing headlights, or traffic officer and incident support vehicles using flashing amber lights. When one approaches do not panic. Consider the route of such a vehicle and take appropriate action to let it pass, while complying with all traffic signs. If necessary, pull to the side of the road and stop, but try to avoid stopping before the brow of a hill, a bend or narrow section of road. Do not endanger yourself, other road users or pedestrians and avoid mounting the kerb. Do not brake harshly on approach to a junction or roundabout, as a following vehicle may not have the same view as you.
As an aside, they may need to rewrite rule 224 now:
Rule 224
Electric vehicles.
Be careful of electric vehicles such as milk floats and trams. Trams move quickly but silently and cannot steer to avoid you.
------------------
Going back to the original poster's intent, the Model 3 has held up remarkably well from such a large impact and it's great to hear that the safety aspects of the Model 3 are as good as advertised.
About 30 years ago we had a car hit our trailer during an overtaking manoeuvre on the motorway which flipped our car. There were three of us in the back all of whom were thrown from the vehicle. My mum broke her back and has had life-long issues with it since. I was thrown under the trailer and broke my left femur, my sister broke her arm. I have no idea how we survived but I ended up in traction for about 3 months.
Most of the incident is still blacked out in my memory. I actually found an old photograph of the post-accident car the other day and experienced near enough a panic attack so I guess it's still buried in my head somewhere. One part of the memory I do recall though is being put in the ambulance and being asked if we wanted the sirens on. I remember saying yes. One of the reasons that they sometimes don't put sirens on is because it can exacerbate an already massively traumatic experience for the patient.
So while I'm sorry that your car is a mess, it's good to know that your wife walked away from it more or less uninjured.