I think a big part of the calculation is whether you can actually claim the 45/25 per mile directly or whether your company will pay car allowance recipients the company car rates and you only get the tax relief on the difference.
If you can get paid the 45/25 directly and an allowance, I think even with the big BIK discounts it'd be hard to make an EV stack up financially as a company car and as you say, privately they're still £££.
All depends on the cars and what you want to drive. Each case is different.
Some companies are mean on their car allowance. My gf worked for a big multinational and she could either have a £400 per month car allowance (so basically not much more than £232 per month after tax) plus 45/25 per mile or could have any lease car from the list up to £750 per month.
People who were quite happy to run a 3 year golf diesel could make money from having the car privately but if you wanted to run the same type of car as what £750 a month got you then no way, even with BIK unless it was a car with stupidly high emissions.
Years ago I had a friend who got paid 50p flat rate per mile, no matter how many miles he did (obviously paid tax over the allowance) and he could basically write off the full value of a new decent car every 3 years so whatever he sold it for after 3 years was his profit (he was doing 30,000 business miles per year for the company)
So there is no hard and fast rule as to which is better.
It will all vary depending on
Amount of business miles
Amount of private miles
Fuel economy
Amount of car allowance
Amount of PPM for business miles
Cost of business car insurance (some can be eye watering, it was for my GF when she was a vet with all the drugs in the car)
Whether you want to run new cars or older cars
Whether you want an ICE car with 37% BIK or an EV with 1% BIK.
You just have to sit down with a spreadsheet and work it out.