Your example was actually a 'xã', not a 'thị trấn'. Someone mistakenly edited it as such.

Anyway, yes, the local people still refer to such places by their old names. In official contexts (newspapers, governmental addresses, administrative documents, etc), the new names will be used. The locals will still use the old names; in fact, there's no requirement to switch over to the new ones yet.

Actually, I'm thinking of restoring them back under the boundary=historic tag. I have an .osm file that I saved of the previous subdivisions before I redrew them all. If you like, I'll send them over to you, and you could recreate them.

Regards,
Tuấn.