I know there isn't a way to log if a player is using MQ. But there may be ways to find out if they are using it or not. I use MQ because it comes in really handy when world building, or to watch players. One of the rules on my server is that MQ is allowed but only for spawn viewing on maps. If anyone uses it for warping, they will be banned immediately if I catch them. I don't use MQ on servers that don't allow it. And I have never once used it for anything other than the maps with spawns.
The reason I am mentioning that I use MQ is that I know some of how it works. I am sure there are some ways to trick players into turning themselves in. Maybe something like making a spawn in an unreachable part of a highly traveled zone that has a name like #Secret_Uber_Quest_NPC. Then all you would need to do is make a quest that uses the quest::write command to write the player names to a file when they hail the NPC lol. Maybe even put a bogus quest on it like hailing it summons some awesome no rent item. Otherwise, they might warn the other players about it.
Code:
quest::write("warping.txt", "$name the $class is using Macroquest.");
I heard that Sony even used chat filters to detect if a player mentioned a unique spawn name that was outside of any trackable range. So, that player is obiously using MQ (or showeq). Just name the mob something funny that will be an extra incentive for people to mention it. Old Plane of Hate used to have NPCs named something like "ShowEQ Users Suck". Of course, the name would probably have to be more unique than that so there is no chance someone would actually say it in everyday chat.