Question about WebDAV MOVE/COPY with Overwrite header true

Hello,

I'm currently working on a WebDAV Server implementation in php.
But i'm unsure about the correct behavior of MOVE and COPY with  
Overwrite true and Depth infinity of a collection to a destination  
that already exists.
What will be the correct behavior if there is a collection or resource  
inside the destination collection that can't be deleted cause of a  
lock or missing permissions.
Will the complete MOVE or COPY fail cause the DELETE on the  
destination failed ?
And if the MOVE or COPY fails should the same Multistatus header a  
DELETE with "Depth: infinity" on this collection would return, be  
returned ?

Regards,
Till Niese