Twig allows the use of the global variable _self to specify the current template : http://twig.sensiolabs.org/doc/templates.html#global-variables

Using ez_render_field it is possible to specify the template that will be used using the optional parameters: https://confluence.ez.no/display/EZP/ez_render_field

If the override is used only in the current template, it would be convenient to be able to code it within the current template and use _self as template parameter.