This transfer presented Mythic with some unique issues. OST may have been one of the lowest population servers, but it still had a fairly substantial active player base and forcing everyone onto one server could have led to balance and overpopulation consequences. Many role-players also had characters of one realm on OST and the opposite on PT.
Mythic's rules do not allow subscribers to play both sides of the war on the same server, so they gave players of PT the opportunity to transfer to VOR as well. Finally, there is the issue of transfering from a role-play server to a core server, where there is less enforcement of proper naming and player maturity.
These issues aside, WAR is a game that requires a large number of players to be enjoyable, so many Oysters (as they're called on OST) are embracing this transfer option (as evidenced by Mythic's account website running much slower than usual today). Those wishing to transfer should read all the rules before doing so, as the process requires character and guild preparation.