As much as I can tell SiteCake stores the content directly in the page. Hence, it would need to have the Hype document with the sc-content available on server side but Hype is run and expanded on the client. Either I am wrong or you would need to exclude Hype’s JS in the edit process and hide the sc-content areas in the Hype mode and pull in the content in to your Hype file. That would be the easy way.
The sophisticated way would be to get SiteCake work on a client side Hype preview and trick the publish process to update a sc-content div on the server.
Update: wanted to give the integration a try but it is closed source. Sorry your on your own.