Str82u - 7:46 pm on Feb 19, 2013 (gmt 0)
In a CMS, many of our pages have "Page Title - Site Name" titles, over half do not, they are simply "Page Title". Many search phrases that return results for those pages without hyphenated titles will have the hyphenated title added by Google because it's in the user's search query.
EX: Page title is "City Widgets" and site name is "Widgets Of The United States". If the user searches for "US city widgets" the title in the SERPs for that page may be "City Widgets - Widgets Of The United States" but when you visit the page you can see in the browser title bar/tab it's just "City Widgets" and looking at the source code will confirm that we only intended "City Widgets" to be the title.
I've never seen titles rewritten to something that doesn't exist in the site though, like "City Widgets - Widgets in Washington" when there is no page with "Washington" in the title.