you should be changing your oil between 2500 and 3500 mls on the street. you should be changing your oil after about every 2-3 trackdays. i think a normal trackday will yield around 200-250 miles, so thats around 500-750 mls per oil change w trackday conditions. so based on that, lets just say that trackday miles breakdown your oil approximately 5X's faster... so just multiply the number of miles you did at the track by 5 and that will get you in the ballpark for approximate street miles conversion.
ie... you have fresh oil and filter in the bike(0 street miles) and you do a trackday(250 miles) that would be approximately equivalent to 1250 street miles(250 miles x 5) so you now have approximately 1250 to 2250 miles of street riding before your next oil/filter change.
this is all really an approximation. the best recommendation would be to change your oil as often as you can afford within those specs.... so for example if i did a trackday then i would lean towards only running about 1250 miles on the street rather than stretching it out to the 2250 mile mark.
keep in mind oils of today, especially the synthetic oils, are absolutely phenomenal. in reality they can handle a lot more abuse than we put at them. You could push oil changes out to 5,000 miles and i still believe the oil would retain its lubrication capabilities. we add that safety factor in there to give us a good buffer zone, bc of the tight tolerances, wet clutch, shearing forces of the transmission, and high rpm that these motors turn. if you know the bikes will need an oil change at 3,000 miles most people wont get around to it until around 3,500 or 4,000 miles so you plan earlier maintenance to compensate.
If you are running a combination of street and track I would highly recommend a full synthetic oil, personally I use nothing but Amsoil for myself and my customers.
the only way to really tell would be to take a sample of oil that has 3000 miles on the street and compare it to a sample that did 250 track miles + 1750 street miles.(which through my little conversion theory, should yield about the same amount of breakdown)
a lot of racers use these guys to do oil analysis for them:
this would be a really cool test!