Yes, Hydra Columnar and PostGIS get along just fine. We've not looked into any PostGIS-specific optimizations yet, but if users run into issues, we'll be happy to investigate.
the columnar "does not support gist, gin, spgist and brin indexes." :-(
and "gist" is important for spatial indexing : http://postgis.net/workshops/postgis-intro/indexing.html