There is no official brushless motor class in ROAR or NORCAR as of yet and it does not meet the motor design rules for modified or stock classes.
There are some tracks and some races where there are brushless motor classes such as the recent Novak race at Trackside.
I have used one in both sedan and oval cars and in general it lives up to the billing as a low maintenance alternative to brushed motors and has good power. The one drawback I noticed on a road course is the total lack of braking action unless you deliberately brake with the trigger - not that you can't drive the car that way, its fast that way too - but in traffic with brushed motor powered cars you have to be very careful not to run over them going into the corners. It was flat out fun in an oval car with 4 cells.
It will be a local thing for a while until enough drivers have them and submit to a spec motor type class - for which I haven't noticed a generally willingness among RC drivers to do in my 17 years of racing.