If an ICE got 35 mpg with gas at $3.10/g...

...then the cost of energy would be $10.333 per mile. In my post above in this thread I cam up with an estimate for an all-EV of a cost for energy inputs of about $0.05 per mile. So if you just did (10.333/5) X 35, you might say that the miles-per-gallon equivalent would be about 72--sort of in the ballpark for your beamer. If the cost for the EV were more like $0.04 per mile then the MPGe would be about 90.

I would think that the MPGe calculation is prone to the same wide variability as gasoline MPG is, based on, e.g., the vehicle model, age, and maintenance history; the driver's habits; the type of driving done, the climate, etc., etc. (which is why some years back I decided to mostly keep track of my energy cost per mile versus MPG).