Yes, you can import your existing Pins (waypoints) and Tracklogs in GPX format for use in BillyGoat. 

Step 1: Email the GPX file to yourself.

Step 2: Open the email on the mobile device.

Step 3: Tap and hold on the GPX file attachment until option sheet appears.

Step 4: Choose BillyGoat from the list of apps

Step 5: Follow the onscreen prompts in BillyGoat to complete the import.