Presently there's a bug in WordPress for those who have a Posts Page set under:

Configurations->Reading->A Static Page->Posts Page

If you will find posts, compared to page (e.g. having a slug known as news) shows the publish, and uses index.php in the theme.

But, with this particular configuration, if you will find no posts, it calls the theme's 404 page. This really is certainly a bug, and it has been posted (Ticket #10822). It ought to be letting index.php show whatever it wants upon !have_posts(), but at this time the page does not appear to become known as whatsoever.

My real question is: it is possible to workaround with this bug without modifying core wordpress files? I'd most probably to some wordpress plugin, theme changes, a custom page template, htaccess changes, etc.

I simply carried out an evaluation for this. It is not really serving a 404, it's using index.php consider no posts are located therefore it falls outdoors from the have_posts(). Are you certain it isn't a wordpress plugin or theme leading to your problem? I examined this using the default theme on the base install of WordPress.

Most theme files have in their Wordpress loop a catch for no posts, i.e.:

<?php else : ?>
Sorry, but you are looking for something that isn't here.
<?php endif; ?>

That could be what you are seeing. Use a custom page template without that text (leave the loop) for yoiur posts page. And check out Reveal Template | to discover what template file you are searching at.