RMAN cannot restore from backupset copied to disk from tape

Attempting to work around an issue with our backup system, I copied the backup pieces from a known-good backup from tape to disk. Then I attempted to catalog those pieces for a recovery attempt. Cataloging those pieces failed.

RMAN> catalog backuppiece '/u01/app/oracle/admin/scripts/restore/filetest/DB_3rn2tp0j_1_1';

using target database control file instead of recovery catalog
ORA-19870: error while restoring backup piece /u01/app/oracle/admin/scripts/restore/filetest/DB_3rn2tp0j_1_1
ORA-19587: error occurred reading 0 bytes at block number 1
ORA-27067: size of I/O buffer is invalid
Additional information: 2

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of catalog command at 02/17/2012 09:37:20
RMAN-06209: List of failed objects
RMAN-06211: ==========================
RMAN-06212:   Object Type   Filename/Handle
RMAN-06213: --------------- ---------------------------------------------------
RMAN-06214: Backup Piece    /u01/app/oracle/admin/scripts/restore/filetest/DB_3rn2tp0j_1_1

Eventually found Oracle Support Doc ID 1111603.1 on the subject. Essentially, no, you can't catalog a backup piece that's been restored from tape to disk because the header information will be different than the file at rest on tape.