My own experience is that they are not picked up by Google Places but if someone is searching for reviews of your company, services or products. We use the plugin on a site called Supercloth Clean. Go to Google and do a search for "supercloth reviews" and you will see our site half way down the page and the stars showing that we have ratings.
That being said check out this Google Places Page, Barbara Oliver Jewelery and underneath her Google Reviews are links to reviews from other sites as well as her own, here. It's not a WordPress site but it might be worth looking at the code and how she has the page setup.
I don't know if it has to do with the number of reviews she has on Google and other sites or if it is how the testimonials are coded, it might be both.
Hope this information helps.