I'm not sure how often this occurs, or if I missed some process to get an updated copy of my account over, but I suggest that anytime (or perhaps the day before) a new build goes to PTS that a fresh copy of characters is done so that players can have the characters they are used to, not ones that are from months ago.
I think this would really help in testing, because much of my gear is different, and even my 2 other toons (other than my lvl 100) are different.

-- Cras

on this last build it looked they were copied about a week before they went live.......jsut a guess

It's standard procedure to do a copy as part of the process of publishing a new build to PTS and putting out a new patch for PTS clients. I believe the reason it wasn't done for build 99 (and in general isn't always done for iterative updates to PTS between a single live update) is to let people who were experimenting with build 97 directly compare their tweaked PTS character between the two builds (rather than have to take their live character and tweak it again).