Apparently so. The reason it’s faster than the M3 round the track is because it can find racing lines where the M3 can’t.
This is in fact BMW’s latest advertising gig for the X5M. They decided the best way to showcase the car’s performance is to show people how it can beat the M3 in a race around Laguna Seca. Granted, BMW is shooting one of its legs, but it does work:
The BMW X5 M and the BMW X6 M set new standards in this segment of high-performance models in terms of acceleration, lateral dynamics, steering behaviour, stopping power, and efficiency. Both models accelerate to 100 km/h from a standstill in 4.7 seconds and stand out not only through the truly impressive delivery of power by the V8 turbo engine providing maximum torque of 680 Newton-metres or 501 lb-ft in the broad speed range between 1,500 and 5, 650 rpm, but also through the likewise smooth and consistent build-up of lateral forces meeting the highest requirements and the most dynamic level of performance in bends.