Will all drivers get the same mileage on the same grade of tire?
No. Mileage is determined primarily by driving habits. Drivers who start off slowly can expect the best tread life. Those who consistently make "jack rabbit" starts and stops and fast tire screeching turns will get the least.
Studies have shown that treadwear for the same tire can be as low as 14,000 for some drivers, but as high as 30,000 miles for other drivers in the same geographical area. Proper maintenance is also important. Under- or over-inflation, unbalanced wheels and wheel misalignment results in uneven treadwear that causes the tire to wear out prematurely.