Quote from FXTraderWill:
They're required to report them within 60 seconds on the consolidated tape. Whether or not they comply is a different matter, but the overwhelming majority of the volume going on in stocks is still going on at the exchange and through ECNs. Reading the tape can be imperfect, but I have several edges and/or setups based purely on the prints and/or open book which work extremely well. If you'd like me to discuss in more depth what kind of trades I get into, I'll start a thread or a PM explaining some recent trades of mine (both failures and successes) to show how what I saw could not have been seen without the tape and how it was improbable that dark pools and large block trades would have had a notable effect on the probability of my setups panning out.
I suspect many insider transactions aren't done through crossing agencies, though I may be wrong as I have no idea what I'm talking about when it comes to actually executing illegal insider trades.