| Sekret_One |
It would make sense, seeing as negative effects such as 'bane' would effect them similarly.
For RAW: in their entries in the beastaries, it says what type they are, say a duergar is humanoid, (dwarf). Therefore it's a dwarf. Therefore, it can do those things dwarves can do (such as trade out racial traits they possess for new dwarf ones, and meet the prerequisite of being a dwarf for a dwarf feat).