The "Directions" button in ServiceTrade mobile will open directions to your current appointment in Apple Maps. Apple previously allowed users to choose alternative mapping solutions, such as Google Maps or Waze. This setting was removed in iOS 9.
There is a workaround, detailed below:
After tapping "Directions" in ServiceTrade mobile and the route is brought up in Apple Maps, tap the car/travel time image near the dropped pin, then tap the upload/share icon in the upper right-hand corner, then tap Routing Apps.
Any routing apps you have installed on your phone or tablet will show up as options. Tapping one launches the respective app with the destination plugged in.