How do electric vechicles hold up in something like this?
Jerrycans for some, tows to Fast DC chargers for others. Class 8 semis should have sufficient diesel reserves for long loiters, even with truckers using auxiliary power units for heat. If not, it is trivial to refuel them on the road with a transfer pump.
But in the case that a car does drain the battery, how difficult is it to get a portable charger to someone? Have roadside mechanics started carrying generators in their trucks now? They probably should, with the appropriate cables.
To your second paragraph, AAA (the tow service) piloted mobile generators for stranded EVs. There was no demand, and the service was discontinued.
There are already vehicles that have been tested in real world conditions. Tesla Model 3s exist with and without heat pump. The difference isn't that large, around 10% more range with the pump in perfect conditions. I've seen people doing tests sleeping in their cars all night and in cold North American winters it's not pretty. With a fully charged battery you will get enough heat for a comfy good nights sleep, 8 hours or so. So lets say in an emergency situation you can stretch it to 12 or so by reducing the temperature. But that's on a full charge! Most cars getting stuck in traffic are not going to have fully charged batteries. It absolutely is a problem with EVs even more than with ICE cars.
Doesn’t appear to be the case.
While you are right about “not well”, the other option can often be “not at all”
The batteries used in most EV’s should always work to some degree, with regards to temperatures experienced on Earth - the batteries & other systems in most ICE can be completely crippled/not work at all under certain temps faced on Earth
Now, you can specifically go out of your way to ruggedize all systems in your ICE so it works to a much better degree than the EV, but the average person is definitely not doing that.
Regardless if you're in a place where this could happen you should have a box of chemical handwarmers, a heavy blanket, food, water, and other stuff in a box for emergencies.
Edit: looks like I'm wrong, much better answers below!
Idling consumes little gas compared with actually moving the vehicle: https://www.energy.gov/eere/vehicles/fact-861-february-23-20...
A 4.2L engine burns 0.39gal/hr under no-load conditions according to the study there for a large sedan. Let's assume that the load of putting the blower and heater on equate to even 1 gal/hr (an absurdly high value, the rule of thumb I can find quoted in a few places tends to be add 10-20% depending on interior size and conditions outside). Let's also assume a fuel tank size on the lower end (~15gal) for this sedan.
This means in the absolute worst case conditions (you're blasting maximum heat the entire time) around 15 hours of operation for a full tank, 7.5 if you had half a tank.
Comparatively, the Tesla, depending on Model, could use as much as 4.8kWh[0][1] under similar worst-case conditions. Modern versions of Tesla and other electrics have or are moving to heat pump heaters, which is encouraging as it will likely be better generally (though this comes with the caveat that they don't work as well in lower temperatures and I believe are supplemented by coil heaters under those conditions).
At any rate, the worst-case electric scenario gives a full-charge length of 18.75 (90kWh useable out of a 95kWh pack in the largest long-range models) or 9.38 at half. Note, this is giving the Tesla an enormous advantage here as I'm going with the largest battery pack possible. With the long range pack available in the Model 3 those numbers drop to basically the same as the smaller-tanked gasoline sedans.
If you have better sources for those numbers on the Tesla idling with the heaters on, these were all I could find quickly.
[0]: https://insideevs.com/news/340327/lets-look-at-energy-consum... [1]: https://teslamotorsclub.com/tmc/threads/idling.139235/
There will always be older or less efficient cars, smaller gas tanks, smaller battery packs, resistive heaters, and people not rationing the energy available to them.
Taking the worst case, and why not because it's cold, and people may be inclined to do more than idle their engine, means roughly an hour per gallon of fuel.
Some ICE cars may only idle for a few hours, others a lot more, depending on what's in the tank.
Best move is to pulse the engine. Start up, idle until the vehicle is really warm, shut down and repeat every other hour or so, depending on the cold and what people have to stay warm with.