The IP User's Guide and Commands manual is located in the Communications Server bookshelf and it explains the FTP subcommands in detail. On the PUT command, one of the manual statements is
If the remote host already has a file with the name specified by foreign_file, the remote host overwrites the existing file. If the remote host does not have a file with the same name specified by foreign_file, the remote host creates a new file.
The "permissions" for the file and directory on the target system (which has files and directories) will come into it. If that gives a conflict, there would be no possibility to "force" a change anyway.