The {exp:pages:load_site_pages} tag is not very well documented in how you use it. Gleaning from system/expressionengine/modules/pages/mod.pages.php, what it does is merges the specified site's pages URIs with the current site's. It does this in runtime - not saving to config in the DB.
The fact that it is a template tag makes it less useful because the first segment of the URL has to be specified, directing EE to the template with this tag and then possibly the second segment could be used in conjunction with Pages URIs. (Haven't quite figured that out).
The problem I'm facing is our landing pages use the first segment for Pages URIs. So for example we have /about-us that hits a page with the designated template. I tried putting this tag on our site/index and on our designated 404 to no avail. How can you alter Pages URI functionality with a template tag when Pages URI functionality is triggered pre-template?
My question is, how in the world can I make Pages URI's from one site available on another site?