I'm not sure if it's possible: Modders have focused mostly on PC Modding,and I'm uncertain somebody has ever tried modding a console apart from the PS2,that means the Canis Canem Edition of Bully.
I'm pretty sure it is possible..But much probably a bit more complicated than PC..
But,for what I've learned,you gotta have the game's console version you-want-to-mod files on the PC,modify them (not idea how,I'm not a modder myself),then save the changes and try out the game....
That above is what I've understood.like a summary..But it's not THAT exact way,I believe there's a pretty big thing in the middle of that.