Using NameMapping Repositry for another Project

Yes you can copy files or merge files.

But essentialy it would be two files

 if you are using same application but testing two funtionalities in your two projects you will have two distinct namemappings for two projects and maintaining  would be double the work.    

so I suggect that first merge two files and share the mapping among two projects.

You can share mapping by right click (new) project, add existing items, and point to merged file.