There was a Scripthook that worked online until a recent update to the game. All public methods that allow scripts to run Online aren't being released (at least that I've seen while reading the Se7ensins thread), which honestly is a good thing. There was rampant cheating with lots of exploding ammo miniguns, invincible players, etc. It would be nice to have a online-capable trainer for car spawning, but people unfortunately abuse the hell out godmode and whatnot.