My teg is "street tuned" and will never be done again, let me tell you why. Its dangerous and hell on your brakes/clutch! You have to do numerous wide open throttle pulls, now think about that for a second. You're doing numerous wide open throttle pulls down a highway or long back road stretch...see what can go wrong here? Not to mention the risk of getting pulled over, for instance last year while out street tuning my car we passed a sherrif with me on the brakes at 140+, he spun around and followed me, luckily I have been behaving in recent years and have nothing on my record currently, so didnt get pulled over. He did follow us for a good 3-4 miles though, making us sweat it out, it worked lol.
As or the brakes/clutch statement, you have to load up the cells through out the rpm range that you are trying to tune. The only 2 ways of doing this on the street is by holdling the brakes and gas at same time, or to slip the clutch on purpose while applying the gas pedal. Thats why people always ask if the shop is using a "load bearing dyno".
You can "street tune" for your start and idle and then take it to a dyno and have it dialed in. My car will be on the dyno April 1st, not because I want to see certain hp numbers, but because I want it dialed in as best as possible.
As for "real world conditions" there is nothing different from being on a dyno and being on the open highway. Any good shop will have a fan blowing in front of the car to replicate you zipping through the air out on the roadways, plus as I mentioned you can put the car under load.