In theory, Oracle backup sets are platform-agnostic as files, but when NBU takes a backup it also takes into account file system attributes and, again, generally speaking, it may not be possible to restore a file with Unix attributes on Windows.
If you do this as part of a migration, I would try to avoid tape as the medium and NBU altogether. Oracle can create a backup to a folder on disk which can be subsequently shared as NFS and mounted on Windows. Then, Oracle on Windows can access these files and will likely restore them. You will need an RMAN script that redefines placement of DBF files because of redirected restore but your DBA would know this as any redirected restore that involves changes to file locations even on Unix would require it.