I don't know of any logfile but what you can do is activate the auditing feature. Here is a link how to activate it: How To: Enable Auditing for a User
Unfortunately the whole Provisioning section is not auditable, you should raise an enhancement request for this so you can't audit if someone is changing a template itself for example.
BUT you can audit "Edit Scheduled Task". If you do this, you see who edits which task, as soon as someone is dropping a device on a task (which is needed for provisioning tasks too). This means an "Edit" is written to the Auditing feature. But be careful, it tracks ALL task changes, not only the provisioning tasks. You should archive them from time to time and clean the entries out in the database.
Hope this helps.