platyping
Sleeping Dragon
Simple, just check the python codes 
There are codes under onCityBuilt:
But there are none onCityRazed.
Conclusion:
Razing the cities do not remove the boosted stuff.
Even if codes are added, there is still one loophole where it will still be screwed.
Building a city on turn 0 will add the boost to the tile correctly.
Regenerate the map, and the boost still remains on the plot with same X and Y...
Since the city was not razed, no codes will be activated even if codes are added to onCityRazed.

There are codes under onCityBuilt:
Code:
if pPlayer.hasTrait(gc.getInfoTypeForString('TRAIT_EXPANSIVE')):
# Places extra food on city tile if founder is Expansive
CyGame().setPlotExtraYield(iX, iY, YieldTypes.YIELD_FOOD, 1)
if pPlayer.hasTrait(gc.getInfoTypeForString('TRAIT_FINANCIAL')):
# Places extra commerce on city tile if founder is Financial
CyGame().setPlotExtraYield(iX, iY, YieldTypes.YIELD_COMMERCE, 1)
if pPlayer.hasTrait(gc.getInfoTypeForString('TRAIT_INDUSTRIOUS')):
# Places extra production on city tile if founder is Industrious
CyGame().setPlotExtraYield(iX, iY, YieldTypes.YIELD_PRODUCTION, 1)
But there are none onCityRazed.
Conclusion:
Razing the cities do not remove the boosted stuff.
Even if codes are added, there is still one loophole where it will still be screwed.
Building a city on turn 0 will add the boost to the tile correctly.
Regenerate the map, and the boost still remains on the plot with same X and Y...
Since the city was not razed, no codes will be activated even if codes are added to onCityRazed.