Well if they don't associate their Parkour training with their tagging, then whats the problem. Parkour is just the training mathod. If they are running away from the police, they are running away from the police. Not doing Parkour. And as far as I'm concerned, if someone who is tagging is running away from a cop, the last thing the cop will think is "Oh yeah, he's doing Parkour!"
To anyone who does Parkour and tags: When your tagging, never bring up the word PARKOUR*. If you ever try to run away and get caught by the police, DON'T MENTION ONE SINGLE WORD OF PARKOUR*.
If you apply to those two rules, then your fine in my book.
-David
*Same goes for any variation of the discipline, Freerunning/ADD/Freestyle Parkour lol/etc.