I know it sounds silly but I have tried it and it does not work.
I wanted to activate the Enterprise wiki page and Project Page (from the Enterprise wiki template) in a normal Site Pages library in a Team site where publishing features are activated.
The reason is that eventually I might want to use the page with the rating box in a normal site that is not an Enterprise wiki site.
Is the error I receive by design? I notice is it normal to add extra content types in a document library but a Site Pages library does not accept further content types that are not Web Part page or Wiki page.
I am using SharePoint online (2013)