Why would ISPs monitor for content they don't own? They have no incentive to kick their own customers off their network for content the ISPs don't own. I'd love to see a source for "everything you've heard".
The whole system is about the RIAA/MPAA trying to force ISPs to do their bidding and how much of the cost they can offload to ISPs. I'm sure ISPs doing the monitoring was on the table at some point and then the parties "compromised" on letting the AA pay for the monitoring.