They do have a bot detection process. I've been banned myself and it is a report driven system. If you get enough reports then WG will investigate your account through actions to determine if your tank is autonomous; which lets all face it is very easy to detect especially with the AFK spawn shooting incidents, the getting stuck and water boarding scenarios, being last tank alive and driving out in the middle of no where while the enemy caps your flag, all of this is happening while your in a tier 8 or better tank.
Their ban process might not be a true software driven game guardian but there is a process to their ban hammer and its usually done by human eyes which makes it worse. That explains why very very very very very few warnings are issued and perm bans are instant one shots.