Using local temporary space first is due to disk affinity. That was introduced in release 7.3. You could disable it by setting _affinity_on to FALSE, but there would be no benefit in doing so.

The failure to use non-local temporary space probably reflects the ownership of temporary tablespace extents by particular instances. V$TEMP_EXTENT_MAP.OWNER has the instance number of the instance that owns each extent. In theory, instances will surrender unused extents that they own when another instance needs them. The failure to do so is either a bug, or could be because those extents were in fact in use, albeit lightly.

We are running Oracle 8162 in OPS mode on SP/2. We have four nodes. The TEMP tablespace has 20 files spread around all four nodes; total size about 40G. Yesterday a query failed because of running out of TEMP space. We looked at OEM and it showed that only the datafiles local to node1 have been utilized.