From the code I posted, it looks like you can package serverLoadSaveFile_Tick and check for if events are being processed through there. Since the last brick is saved to $LastLoadedBrick, you can simply do $specialBrickGroup.add($lastLoadedBrick); to move it to that group if a certain event is processed.
Be very careful about NTNames and spawn point bricks though. Since these usually come before events, you'll have to unregister them on the $LastLoadedBrick's original brickgroup and re-register them on the $specialBrickGroup.