I have been exploring some CMIS functionality and when I tried to create a new document I ran into some exceptions. I found a related JIRA in the opencmis-client-api component (https://issues.apache.org/jira/browse/CMIS-246) that pointed me in the right direction. I checked the TypeManager.java file in the fileshare component and noticed that the updatability flag was set to READONLY.
I assumed that it should be set to ONCREATE so I tested and it worked. I got one followup problem though, in FileShareRepository.compileProperties the typeId is excluded from the incoming properties and added at the end instead and this will cause the required properties validation to fail. I did the simplest (and probably the ugliest) thing and commented out the removal of the typeId property in the loop.
See the patch if you are interested.