If you're not sure, just get new ones. I mean, is it worth it to spend money on bodywork and other parts just to save a few bucks on tires?
For what it's worth, I would consider my tires pretty shagged after two trackdays, no matter how much tread is left on them. I guess it depends on how you ride, but if that's you in your avatar and you are doing decent laptimes in the A group then I would consider new ones if I were you. Tires are not a place to look when trying to find places to save money.
Depends on what tires they are. My pilot power race's that I bought for my 848 lasted only 1000 miles after a track day. Its very hard to tell if a tire is good on the street because most of the time, other situations cause the bike to slip which would be an indicator of bad tires.
My rule of thumb is quite simple; once the tires have been squared off from all the highway riding, I buy a new set. I also take into account age and tread wear. There is a point where the tires are just not safe to ride on because of the flat spotting.
In your particular case, my generic answer would be; Keep riding it until you know the performance of the bike is being hindered from the tires or they're REALLY old (5000 miles/2 years)
Think about it - would'nt you want the best insurance against a crash, especially on a track day where a good vs marginal tires might save your ass from a stupid mistake. If YOU think your tires might be marginal, new tires are really cheap insurance compared to injury or the cost of repair.