Client IPS and Network IPS uses two different approaches. A network IPS usually detects more, but with higher FP rate. It also protects your entire network and not just the clients. The Client IPS is more tuned to protect against known client attacks and block malware from communicating out.
There are a lot of things happening with Symantec ATP. ATP allows email, SEP clients and Network to share data.
Integration between SEP and BlueCoat appliances are on the short term roadmap. Other vendors have been mentioned, but it´s all still not 100% clear which will be supported. I believe it will be more file data that will be shared and not IPS functionality.
E.g bluecoat detecs a bad file on the network and tell all SEP clients to block it locally.
ATP:Network is licensed seperatly.
https://www.symantec.com/content/dam/symantec/docs/data-sheets/advanced-threat-protection-network-en.pdf