Right, so the TempDB usage is not due to the reorg using TempDB, it's the snapshot isolation and the row version store.
To be honest, I'm not 100% sure how the row version store interacts with multiple files.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability