Two things. One, there's already a function for loading a save file and you don't need to hack up the literal load save file function.
serverDirectSaveFileLoad(%fileName, 3, "", %ownership)
So, this makes your life easier, but %ownership can only have three values: 0 loads as host, 1 loads as default ownership, and 2 loads as public. So, since you want to use a weird name like BrickGroup_Platforms instead of following the nomenclature the game uses, none of these will do what you want automatically.
So, secondly, there's a solution to this, but it's a little roundabout. Load the bricks into public and then instantly transfer them into the correct brickgroup:
while(brickGroup_888888.getCount() > 0)
BrickGroup_Platforms.add(brickGroup_888888.getObject(0));