- Coal power plant areas: Maritsa-Istok (what about others?)
The second largest is in Beloslav municipality, near Varna which voted 55.5% "yes". The third largest is in Bobov dol and there are also large ones near Sofia and Pernik. So the rule doesn't seem to hold up very well. Then again, the Maritsa Istok complex is old, polluting and will probably be among the first to go if it ever comes down to closing unnecessary power plants. And without the power plants, the coal mines there will probably have to close as well - their current purpose is to provide coal for the plants. That is probably not the case in the coal regions in western Bulgaria.
I have some more coal area figures:
Bobov dol town (coal mine & power plant) 64
Babino (coalmine, Bobov dol municipality) 40
Mamlovo (coalmine, Bobov dol municipality) 73
Katrishte coalfield, Kjustendil municipality 75
Gabra (coalmine, Erin Pelin municipality 53
The other coalmines I came across in my internet research are in Bojchinowzi municipality, Montana province, which according to your map voted over 70% yes, and in a Turkish minority area in southwestern Shumen province (also > 70% yes, but that may be due to the Turkish vote).
A pretty obscure picture - some coal areas voted quite strongly against Belene, while others either did not care or, possibly, even would be happy if the mine closed rather sooner than later (e.g. Katrishte, which is open pit and has recently been privatised). It is also interesting that of the two coal mining towns near Bobov dol, one - to the southwest - voted "no", while the other - to the southeast - voted strongly "yes". Am I right to suppose that winds are primarily blowing from the norht-west?