The fuel depots are now active and operational in PT.
You will see fuel depots dotted about in the game, and they appear as an entity on the navigation screen. They will all have the same graphical image so are easy to spot.
If you approach the fuel depot, you will be presented with a screen like this:
The process is incredibly simple. If you have fuel in the depot, and space in your tanks, click the green button to fill your tanks.
Not a lot more to be said.
Any issues, please let me know.