I was browsing through some of the old video archives and came across a video I had recorded back in 2010 on how to integrate AgilePoint process with BizTalk. Though the video shows few of the AgilePoint V5 legacy components like Visio based designer and uses InfoPath as form technology, the concept remains the same even in AgilePoint NX albeit you would be using new web based App Builder to design the process model and perhaps even use AgilePoint NX eForms as your form technology.
The concept behind the integration is that starting Biztalk 2009, Microsoft introduced support for WCF enabling BizTalk endpoints and as you know AgilePoint has capability of consuming any WCF service endpoint using its generic WCF connector.
I have covered the end to end scenario shown via a sample application in this video. I will perhaps convert this to AgilePoint NX demo sometime in future but as I mentioned concept remains same between AgilePoint V5 and NX.