Multi-location Groups are able to export Facebook, Google Maps, Yellow Page, and Yelp Reviews in the Multi-location Business App dashboard.
In Partner Center > Go to Accounts > Multi-location Groups > Click at the end of the row > Select 'Open Multi-location Business App'
Once on this screen, click 'Reputation Overview' to access the data table for the group
To export reviews for the group, click the at the end of the table headings > Click 'Export to CSV'