Google will now parse certain microdata (for example reviews) on your web pages and display the info in search results. They call this Rich Snippets
I am wondering is this page specific or domain specific?
I keep all my reviews on a separate review page thats linked to from the home page. But my review page itself is very unlikely to be displayed in a search result, more likely to be displayed is my homepage or product landing page. But being that the review microdata is not on these pages (but is on the website). I am wondering if the rich snippets will be shown for these pages?
They're tied to the page, effectively; a result which returns the homepage won't include content from another page. As with any other organic ranking scenario, Google aims to return the best individual page for a query; as such, if it percieves your homepage to be a more authoritive resource and result for the search query, it'll return that rather than the page containing the microformatted data.
I'd tentatively suggest that the wider problem is one of value attribution, and that undertaking some page-level SEO in order to clearly signpost content/context, and to ensure that content is distinct and relevant at page-level (and in one place for one topic) might help.