Does SBC intercept only successful calls or all call attempts?

Hello.

I noticed that SBC LI does not intercept unsuccessful call attempts, if there is a routing failure on SBC itself then it does not send call data via X2: for example if outgoing SA is out-of-service, or there is no proper local-policy, or there is failure on Rx - in general, if SBC generates the response code 4xx, 5xx by itself. One the one hand an Agency might require the X2 data about all activity of the target subscriber. On the other hand, if SBC sends to X2 info about any given INVITE, any given DoS attack will also trigger flood on X2. What do you think, is it correct behavior?