r304ndy, the fuse plugs are activated by temperature not pressure. After a high energy RTO the heat from the brake soaks into the wheel structure. Above a certain temperature level, the tensile strength of the wheel material starts to decrease. Eventually the wheel strength will degrade to the point where it can no longer contain the tyre pressure, at which point structural failure of the wheel occurs. To avoid such a failure the fuse plugs are set to release the tyre pressure before the wheel temperature reaches the critical level.