PJ2:
Anyone who operates in Russia or has recent experience, can you clarify?
Sorry I cannot claim recent experience but last time I went to Russia it worked as advertised by the current AIP paragraph you published.
Any clearance below the transition altitude is an height above the runway threshold. Foreigners generally are given the QFE in millibars by ATC. It is also very often appended in the remarks section of otherwise standard METARS but sometimes only in mm Hg.
DJ.