In response, we have:

1. Archived the predecessor series (reference year 2010) by renaming with an "_10" specifier, by marking metadata as discontinued, and by segregating in the catalog. 
2. Created one-for-one replacements (ref year 2015). 
3. Replaced the current-priced series in the same way, since they are subject to revisions of other kinds.
4. Refurbished metadata where necessary. 
5. Transplanted global concept aliases.
6. Refurbished the catalog.

Notable properties (for full list, see Mnemonic 411):

• Currency reference year: Changed from 2010 to 2015
• Start date: Unchanged

The active series reside in the historical catalog: 

• Bulgaria » National Accounts » by Expenditure  » Quarterly » Chained prices | Current prices 
• Bulgaria » National Accounts » by Value Add  » Quarterly » Chained prices | Current prices 

and include, for example:

• NACEFCUQ.IBGR    = National accounts: By expenditure - Final consumption expenditure - Total, (Mil. Ch. 2015 BGN, NSA)
• NACSGVACNUQ.IBGR = By production - Gross value added [GVA] - Construction [F], (Mil. Ch. 2015 BGN, NSA)
• NALSGVAAFUQ.IBGR = Production approach - Gross value added [GVA] - Agriculture; forestry; fishing [A], (Mil. BGN, NSA)

References

There is no specific announcement of the redefinition, but there is a footnote in each press release regarding "chain-linked estimates of the GDP components based on average 2010 prices" that changed to "2015" between the 2019Q2 and 2019Q3 editions.