This week I encountered where your content type is being pushed from hub to Site Collections, but is not getting pushed down to various lists and libraries in the site. After extensive testing and fiddling and renaming, we got it sorted. Some of the sleeper reasons that are completely unexpected is if the child content type is sealed or set to read only the push down fails! You can read more about push down operations at the following link: http://msdn.microsoft.com/en-us/library/ms442695(v=office.14).aspx
There are some ULS log entries which relate to pushdown operation failures as shown below. Turn up Diagnostics Logging for unexpected and verbose entries in the SharePoint Foundation General section.
SharePoint Foundation General 8nca Verbose Application error when access /_layouts/fldpick.aspx, Error=The content type "System Page Layout"
at "/" is sealed. The content type "System Master Page" at "/" is sealed. The content type "Office Data Connection File" at "/" is read only. The content type "Universal Data Connection
File" at "/" is read only.