RMAN backup set, nothing else, how can I duplicate?
If you know the sid name, you can copy a pfile over and edit it to change the values to match the database name. Make sure that you set B_CREATE_FILE_DEST to where you want the data files. 

Then do a startup nomount on the database. In RMAN do "CATALOG START WITH '/full_path_to_your_backup';" You can then use DB_FILE_NAME_CONVERT to convert the file names to be in the right directory.

You can then try to restore a control file. try list backup; and restore the oldest control file. Mount the database and try to restore the database.

It could be that the reason why the people who gave you the backup are avoiding you is because they know the backup is incomplete. But you have to try to restore what you can, then at least when you go back to them you can ask a more specific question.