The problem with such systems is once the enemy suspects they are compromised they either turn them off or replace them. Perfectos never lived up to its potential for this reason. The main user 100 Group RAF, had alot of difficulty turning Perfectos intercepts into interceptions. Their main ESM was Serrate a system that tracked SN 2 radar signals.
The same goes in later wars. Once the enemy knows you are tracking a particular system they will adapt and you are back to square one.