haha... administration is perhaps the most powerful anti-cheat tool out there... Im guessing those that are learning coding adapt q3 aimbots to trem, but those experienced enough make their own. Also for human aiming, its not a hard thing to do, you just make it aim behind the target slightly, which will seem / appear to the target that you are a good player but cant get every shot in. This bot doesnt exactly do human aiming, but there are ways of doing it that a few people know.
Sometimes bots that have added human aiming, seem a lot like the player, because the aiming isnt jerky, its rather sluggish, and smooth. It also doesnt aim thru walls, even if you can see the target thru walls. So one way or another, there are ways of masking up (or at least temporarily) the use of an aimbot...
I think the only thing Trem can do, as null said, is detection. If something is dependent on a variable, then trem scans the startup client, and if it finds something, it attempts to detach it, if that fails gives an error and shuts down. They do this with other games like GunZ, with X-TRAP (AKA X-Crap)