I wanted to see, if a building-produced strategic resource, that is only available for the city but not for the trade net of a civ, will appear twice in the city screen and therefore I made the following test with the R17 Preview 2 version of your mod in Debug Mode:
The steam engine and the power plant both need coal to provide the virtual strat. resource Electric Power (that is not normally available in the game) to that city and I set this resource to give 3 shields to that city. The increase in production for the steam engine is 25 %, the increase for the power plant is 50 %.
The resource Electric Power appeared only one time in the city screen (what is good), but the shield bonus was added twice. Interesting is, that in this case no letters appeared for the transformation from coal to electric energy (what in my eyes is good, too, as the shields behind both buildings are enough to show the special characteristics of those buildings).
On the other side the screenshot shows, how quick an avalanche in production capacity here can be created. A solution for the replaces-all-other-buildings-with this-flag slingshot would be really good.
Another understanding of this test was, that a building with one of the "virtual" resources in its prerequisites (at least when not available for the trade net) and a setting, that the resources must be in city radius, could never been built, even when the city is directly located on the tile with the resource, that is transformed to that virtual resource and all other prerequisites are full filled. It seems that, if one of the needed resources for a building is a virtual resource, the flag "must-be-in-city-radius" should not be used, as such a building can not be constructed.