but when anticheat is not enabled, there is no way wondering that some n00bs use cheats. (why n00bs? I think decent players do not cheat).
But MTA:SA may not be as hacked as for example counter-strike, because it does exist for only a short period of time, so not many cheats and hacks were made), so there is not problem with cheating on anticheat servers. I have not seen MTA blue code and most probably I won't , so I can't tell how it does handle cheating attemps etc.
But when you take other games, for example the aforementioned CS, there is high probability that online players will cheat even on anti-cheat servers, because it is endless loop the dealing with cheaters. New cheat is found, it becomes available, anticheat dudes will examine it and block it. Then another cheat comes, another anticheat comes.
I hope for the good of all of us that MTA:SA servers in the future when it will become more popular won't be as crammed with cheaters as the other popular games are...