They may not need to have been arrested. Depending on the program, it may be all up to the prosecutors office if you have lived up to the agreement. Basically they have copped a guilty plea and their records will be scrubbed if the prosecutor thinks they lived a good life for X number of months. If he does not, the original case is reinstated.
I'm no lawyer, that's fer sure. And I may be speculating on this completely out my a$$. Mrs. abb says I do this often, LOL.
However, look at this carefully. Even if Nifong "says" they didn't live up to the terms of the agreement, what did they do? They were at a party? Who says? Kim? The Lax player's lawyer will say, "I don't believe her. Put her on the stand and prove it."
Now all that said, I'll quote Jack Nicholson from "A Few Good Men." "....I'm just spitballing here..." LOL!!