That article:
https://ftb.gamepedia.com/GregTech_6/Stones_and_Minerals#Ores
says
GregTech ore blocks do not work exactly like other ore blocks. Most mods treat their ores as single blocks, with nothing special to them except for the few that must be harvested with Silk Touch or can be mined with a Fortune pick to increase yield. All GregTech ores are non-ticking Tile Entities, defined not by block ID or metadata but by TileEntity data. Each of these TEs contains only two variables: the internal ID of the ore, and a True/False boolean indicating whether the ore block was placed by world generation or by other means. This is mainly used to determine whether or not a Small Ore’s drops can be enhanced by a Fortune pick. Their being TEs though has some unfortunate consequences: not all mods are prepared to deal with TE ore blocks, and so GregTech ores ARE NOT ALWAYS MINED by other mods’ AUTOMATED MINING systems (for example, for several months, the IC2 Miner could not mine GregTech ores), or may be replaced with useless Empty Ore when moved by other mods (such as the Twilight Forest Miner’s Tree, or in the pit of an Applied Energistics 2 meteor). The rendering of GregTech 6 ores is greatly improved over previous versions. Ores will no longer display telltale rendering artifacts when viewed at steep angles, nor will they noticeably interfere with smooth lighting and shading, affording them a much more natural look. (However, OptiFine’s modifications to shading may still make them stand out.)
Can a BC Quarry mine GT6 ores?
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BC sucks, why not use RFTools? 
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Buildcraft should be able to mine them, I never got reports stating otherwise and people like Buildcraft Quarries, I would have gotten reports for sure.
Anyone know the answer 100% for sure?
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The answer is: yes
Source: recently mined a diamond vein, apatite vein, lignite coal vein, chromite vein and a cassiterite vein with bc quarry powered by 4 ev lithium manganese batteries.
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Can confirm, no issues.
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