According to the 8.2 manual you can:
You can restore databases created on a DB2 Version 8 32-bit 3 Windows platform to a DB2 Version 8 64-bit Windows platform, or the reverse. 3 You can restore databases created on a DB2 Version 8 32-bit Linux (Intel) 3 platform to a DB2 Version 8 64-bit Linux (Intel) platform, or the reverse. 3 You can restore databases created on DB2 Version 8 AIX, HP-UX, or the Solaris Operating Environment 3 platforms, in 32-bit or 64-bit, to DB2 Version 8 AIX, HP-UX, or Solaris Operating Environment platforms 3 (32-bit or 64-bit).
7 The restore utility can also be used to restore backup images that were 7 produced on a previous version of DB2 (up to two versions earlier) as long 7 as the word size (32-bit or 64-bit) is the same. 7 Cross-platform restore operations from a backup image created with 7 a previous version of DB2 are not supported. 7 If a migration 7 is required, it will be invoked automatically at the end of the restore operation.
Andy