Yes, it is possible to add retargeting pixels to a review pop. 

Follow these simple steps: 

Step 1: Add a Business to Review Pops 

Step 2:  Navigate to the Review Pix Editor and find "Pixels" Button

Step 3:  Enter the "Retargeting" code that got generated in your preferred Ad Placement system (Traffic Fuel, Facebook Ads or Adwords) into the tracking pixel field or setup multiple pixels in the "Set up multiple Pixels" tab. 

Step 4: Save your settings and click next