IBM Connections is built on an open platform. So open that you may integrate almost everything!
In the demo below, Michel from e-office demonstrates how you can use the Google App Engine to push events from Office365 into the IBM Connections activity stream. You can take a document and upload it to Office365, check-in, check-out etc and visualize from IBM Connections. You can even use the embedded experiences concept that IBM invented to interact with Office365 and preview files directly from IBM Connections.