As a TP, my upgrade rate from Y/S/M to Business is around 50% flying mostly TLV-NYC.
Been doing this for over a decade and have had maybe 2 or 3 op-ups - nothing impressive.
LY policy is to upgrade status pax with the right type of tkt based on availability in F and C, not based on overbooking in Y. The only way an F or C seat remains unoccupied is if there is nobody eligible for the upgrade.