It might be just a coincidence, but I noticed that whenever I take a tech that reveals new resources, they appear only around my cities.
Is it planned that way?
Because if it is, that means that a good strategy will be to delay the tech until you spread out a bit, which sounds like a bug.
Also, will I be able to see and/or use resources that were revealed by my enemy? will he see my discovered resources if he doesn't have the relevant tech yet?