That's strange... this should have worked. I changed the data from this:
cepObjectInfo.NearbyTerrainRequired
to this:
cepObjectInfo.NearbyTerrainRequired and Locale.ConvertTextKey(cepObjectInfo.NearbyTerrainRequired)
This should have displayed...
Oh wait, I needed to fetch the description of the terrain. Try this in Tools/TooltipWriter/TW_BuildingStats.sql and see if it works:
cepObjectInfo.NearbyTerrainRequired and Locale.ConvertTextKey(GameInfo.Terrains[cepObjectInfo.NearbyTerrainRequired].Description)
Edit: Hmm wait no that won't work... the lua file should have already converted it from terrain type to a description. Hmm...
Edit: Oh duh silly me! I was changing NearbyTerrainRequired, which has a bug, but the one you're talking about is ProhibitedCityTerrain, which was also bugged. I've fixed both of these for v3.5.2. I missed this because of a third bug: I placed ProhibitedCityTerrain in the Abilities section, but it belongs in the Requirements section, so I was looking in the wrong place.