How does Configuration Owner & Subscribing an OU to a Regime affect tax classification codes?

We have upgraded from 11i to R12.1.3 and wish to continue using the STCC regime determination set and tax classification codes for the time being.  This means tax classification codes will either default as per the Application Tax Options defined, or users will manually select the appropriate code at transaction entry.

All 11i tax codes have upgraded with Configuration Owner = the Operating Unit in which they were originally defined.  Even though OU1 and OU2 are subscribed to the same US-Tax regime, they do not share any of the tax classification codes that have been defined.  OU1 only sees their tax codes in the list of values and OU2 only sees theirs.