meta title cannot reliably be put inside a template used by the template plugin. Since meta title info is gathered in the scan pass, which does not look at the template a page includes, it will not be seen then, and so other pages that use the page title probably won't use it. (Barring luck with build order.)

Update: This also affects using tags from templates.

There is a simple fix for this, just add scan => 1 when registering the preprocess hook for the template plugin.

However, the overhead of this has to be considered. It means that, on every scan pass, every page containing a template will cause the template to be loaded and filled out. This can be some serious additional overhead.