I have the same issue with 2.0.33 under WP 3.6.1 and 3.7.
Ah. echo get_post_meta(get_the_ID(), '_wpbdp[fields][$fieldid]', true); works. Well, shouldn’t $listing_id instead get_the_ID() work either?
This does not work any more, the function does not exist. And with wpbdp_formfields_api()->get_field($fieldid) I get nothing.
This issue also exists with 2.6.4.