US probably has listening devices all over PRC along with a ton of CIA operatives. Some of em might be right inside the CAC hanger cleaning & painting the J-20
. But, installing RADAR? I seriously doubt it.
Well, I'm not so sure about that. If the US had enough CIA operatives working in key facilities throughout China, they would have no problem knowing the progress of China's military modernization. However, the fact is no one in the west knows exactly where China is in terms of their weapons development, etc. hence the constant pecking on transparency. So I doubt it that the US has many operatives on the ground.
Additionally, the intelligence community in the US admits itself that one of the biggest weaknesses within the intelligence community in the wet is that they lack people on the ground. They become too dependent on technology, such as satellites, etc. if they can't even put enough agents on the ground in Mideast, how do they do it in China, which traditionally has been thought to be the most difficult to spy on?
About listening devices. I believe both China and the US do it to each other. It is a cat and mouse game. You put something in, and I will dig it out. And I put something in place and see if you can dig it up in time. While you spend time looking for it, I collect info... I don't think any side expects to have a listening post in place and thinks that his place will be safe for an extensive amount of time. Everyone knows that these places will be discovered eventually. They just hope that it can get something useful when it is still in place.