May be earlier it was allowed, its in RLWL now..Check out once again but AFAIK tatkal booking is not allowed...If you see the CKWL in GNWL quota is different, usually tatkal quota is same for all stations but in some trains,some strecthes tatkal booking isn't permitted so it comes up as RegretCKWL/1...If its WL normally it should proceed further, even PT is not allowed for RLWL quota.