When I finish researching a tech that unlocks a stronger version of watchtowers (lookout towers or remotuscope factories), some of my existing watchtowers are instantly upgraded to the new version...while others are not. No obvious pattern to which ones get upgraded, except that it seems to follow region boundaries (either all or none of the towers in a single region get upgraded).



For example, in the attached save, I've just finished researching Enlightened Trade. My capital region Moch now has a Remotuscope Factory (free upgrade), while the neighboring region Mesan still has Lookout Towers.



EDIT: Frogsquadron - closing duplicate, please continue the discussion in this thread.