If you are coming from zen cart / oscommerce, my first attempts to migrate the tpl files to a php/smarty hyrbrid were successful this evening.
compare: _bit_commerce/includes/templates/template_default/templates/tpl_modules_checkout_new_address.php
to: _bit_commerce/templates/new_address.php + _bit_commerce/templates/new_address.tpl

Eventually I will get all of the SQL removed from the templates and migrated into the _bit_commerce/classes/ like a sane piece of software.