My guess(since there is a dearth of documentation at this point) is that it is token based. When you say a file requires locking it records that the file needs

My guess(since there is a dearth of documentation at this point) is that it is token based. When you say a file requires locking it records that the file needs to be locked and that you currently own the lock. Then as you push, knowledge of the fact that this file needs a lock is spread. The only other option I really see working is having a designated lock node, so you are centralized only when you need to do locking.