That's what you do not understand.
Every countries satellite comes with proprietary software, in the simplest term, every satellite system is scrambled so no one but you (Or whoever can access to it) can access, to access it, you need to be able to descramble the signal. Which mean you need to have a set of code that written somewhere in a ROM chip with your device to descramble that signal.
Again, you are not talking about commercial satellite like the one MLB used to relay live World Series game, you are talking about Military Guidance satellite, I don't think when Russia is building those military satellite they would have built it in a way it can be share to Iran in mind, otherwise YOU CAN ALREADY ACCESS IT. Which mean unless Russia wanted to share that code with you, which most likely the same piece of software that was used across the entire platform simply because no country is dumb (Or smart, depends on how you see it) to have each satellite have different proprietary access. Which mean most likely if you get access to one, you get access to ALL of their military satellite.
Also, GPS, GLONASS and Beidu is "Commercial" Satellite because normal folks like you and me can access to it, sure if your device have the source code for all 3 you can access to all 3, which you can, with a price, but as I said, we are talking about Military Guidance system, not commercial system, do everyday American get access to Military GPS system which most people don't even know that existed??.