[Detective]

it is possible. Include the file wp-blog-header.php in the first line (after <?php) of your config.php. So, in every template file that calls bb_get_header() and bb_get_footer() you can replace them with get_header() and get_footer().

In this way you’re loading the WP header and footer … and if you want to include some CSS specifically for bbpress you’ll have to do it by means of a WP plugin or editing wordpress’ header files.