bp can be changed for wl tkts as well. the only rule that varies in case of wl tkt is issue of duplicate tkts. duplicate tkt cant be issued for wl tkt. bp can be changed for wl tkt. as i said, the clerks find for excuses not to change bp. some excuses being-
1 tkt is in wl
2 quota changed...remote to gnwl...so wont do it
3...
more... can only be changed from the zone that train belongs
4 tatkal, bp cant b changed
etc but in all above scenarios bp can be changed if TKT PRESENTED TO PRS 24 HRS BEFORE DEPARTURE OF TRAIN FROM SOURCE.