Mike Blumenthal reports that Google has updated their local business reviews guidelines around when you can use the schema markup on the reviews and when you cannot.
Here is the new list of guidelines:
Snippets must not be written or provided by the business or content provider unless they are genuine, independent, and unpaid editorial reviews.
Reviews must allow for customers to express both positive and negative sentiments.
They may not be vetted by the business or restricted by the content provider based on the positive/negative sentiment of the review before submission to Google.
Reviews cannot be template sentences built from data or automated metrics.