Have you checked the documentation? -- http://www.oracle.com/technetwork/documentation/applications-167706.html
I'm not aware of any doc that shows this kind of integration between the two modules you mentioned above, so I would suggest you log a SR and see what Oracle support (product teams) would advise.
We integrate our iLearningPLUS application with other shopping cart products such as Digital RIver, Cybersource, Pay.gov and others. While we have not done iStore before it theoretically would be possible to integrate the applications with the product extensions we provide.