OK current day FAA etc use RADAR only as ground approach only. Long range is done by the airframe having a continuously active IFF transponder, that tells the FAA everything about the airframe, ie speed, altitude etc. Military Airframes can turn their IFF off and other nice tricks. I know this because in the days in the USN while my ship was tied to a pier in Long Beach Naval Ship Yard (LBNSY) my new RADAR/IFF system was jammed LAX. Took them two weeks to locate us.
Usage of High Powered RADAR in urban areas is a major No No, as when the "Sea Gull Cooker"'s interlock was defeated and it rotated at full power ie 1+ Megawatts, in Great Lakes, Ill. The resulting damage was extensive to say the least, the "Sea Gull Cooker" was removed after that.
Yes the Ballistic Missile Early Warning System(BMEWS) RADAR that can be used to track objects are space can do it, but look at the "Dead Zone" in front or around one.
One futuristic item lacking is LADAR units.
As for drones roaming around in Air Space, a simple IFF interrogation will determine what if anything is done to said drone. Usage of Gas Lift Drones gives the ability to "look down" into Air Space, most RADARs are not much bothered with by air pollution.
Typically a low to medium power RADAR would constantly scan the Air Space, any thing detected it is IFF interrogated. Any IFF issues cause the usage of focused High powered RADAR/LADAR units being used to gather more detailed target information.
And Yes SR4A ECM/EW are magic, due they can jam only using software not hardware like in Real Life. Yes I loved the SR3 rules for EW/ECM but that is what I did in the USN so I had a Leg Up on understanding the rules.
Smart EW/ECM of today can adjust very quickly to changing frequencies etc. Avoiding jamming friendly RADAR's requires some solid communications/networking between the jammer and the RADAR's.
For a flying drone one would need something like the Spoof Chip for vehicles to get around IFF interrogations.