Some changes have been made since this thread was posted. For starters, AFK detection has grown to where it'll catch accounts that just idly click in the base to avoid the auto-disconnect for inactivity. They will get LeaverBuster penalties for doing this. Unfortunately, this basically just means the scripts have to be a little more sophisticated to avoid that (which they mostly are now).
Also, there was a Riot post a little bit ago talking about working on something to quickly detect botting on accounts. I'm honestly not sure if it's implemented yet or not, but I know it was being worked on.
However, the whole battle against bots leveling accounts is really a losing proposition for Riot. The people writing the scripts are going to be constantly improving them to try and avoid detection, which also means Riot will have to constantly evolve their detection systems to catch the accounts they're missing. But Riot is stuck essentially in a reactive state on it, because they can try to predict what the scripts my try next, but inevitably some will always get by.
On top of that, it's also always going to be faster for new accounts to be created than Riot could possibly ban them out, even with a system that detects these within a few games. It's basically just a giant game of whack-a-mole.