Hi Chris,
I just encountered the same question.
To me, it seems that table VBSET is no longer filled mit tax data from parked documents since our upgrade to ECC 6.0 EHP7.
Users discovered this issue first when reporting parked docs with RFBELJ00.
Unfortunately, I couldn't find any sttement from sAP that this table is no longer supported.
Did you get ahead with your issuemeanwhile?
Regards Klaus