It is certainly not trivial, and definitely out of reach of most nation states out there. I'm sure U.S. at least tries to keep track of Russian mobile launcher

It is certainly not trivial, and definitely out of reach of most nation states out there. I'm sure U.S. at least tries to keep track of Russian mobile launchers, but to which degree it is successful we wouldn't know for sure. And pretty certain Russia would have problems live tracking launch vehicles (if the USA had any).