I use control file backups and when I restore I place the pieces into the locations where they were originally created during backup. Sometimes this is another machine and I have to create the exact paths or make it appear so with soft links.

I would expect there is some way to inform RMAN without doing this but for now it works and thats what I do.

Newname seems to apply not to backup pieces but to restored data file locations i.e. .dbf not .bak