Units can teleport between bases containing Psi Gates
The Psi Gate is really a luxury item. It comes at the top of the tech tree, when your strategy should be well on it's way. If your faction is centralized on one landmass, the Psi Gate doesn't do much that a good network of Mag Tubes won't do. If you're trying to mount an invasion in deep enemy territory, orbital insertions ( depite some drawbacks of thier own ) are your better bet. The Psi Gate can be useful in transferring resources from one continent to another in an effective fashion. If you want to expand to an unsettled continent late in the game, establish a single base as a beach-head, build a Psi Gate, and use it to transfer formers and colony pods from the center of your faction to the new lands. This will allow you to rapidly settle the new territory without risk associated with sea transport.
