They way it will work at launch and currently works with the Beta is that if you have the account that has that name on P99 you can create a character with that name on R99. Some other things apply that make the name up for grab if the character hasn't been logged on in x number of days.
I know it works like this, when R99 beta came up I tried creating Atmas on a different account than the one I play with Atmas on P99 and it wouldn't let me. I was able to create it on the same account though. I also was able to create a character named Knuckle because no one has logged in with that toon in forever.
The complete thread:
http://www.project1999.org/forums/sh...ad.php?t=50397