Sure. A global setting is better if you want all players to benefit from the discount. Otherwise, the simple but tedious way is to pay a visit to the map file, do a manual search for every individual city and plunk down an extra line of code for the new building. It's a pain but it works. I did something of this nature in my current project -- a partisan hideout preplaced in each foreign occupied city, which produces some significant penalties instead. The partisan hideout goes away when the city is captured by enemy. It's the same idea really.