I am not actually sure, what you are referring to: Locking or versioning. In case of Versioning, there is no lock owner, as checkout only sets the checkedOut property. In case of Locking, the specification is quite clear in section 8.4.4 Lock owner, that the lock owner is set to the value of Session.getUserID(). There is now way to change this.
btw. the jcr:lockOwner is for information purpose only. if you are refering to the 'lock holder', then there is a way to change it by calling: Session.removeLockToken(String) on the session that created the lock. and subsequently: Session.addLockToken(String) on the other session, that should be the new lock holder.
