The Deepsea Metro is dependent on power from two sources:
The Solar Generator (the panels that sit just under the surface of the NILS Statue) powers the electromagnetic field generator, which distorts the space inside and around the Metro, giving it its strange visuals. It also powers the Statue itself, which houses Commander Tartar's mainframe, and the array of servers that allow him to generate the Sanitized (The Nature of Tartar, 'Sanitized' Creatures and Spatial Distortions).
The Power Orbs are stored throughout the Kamabo Corp complex and the Deepsea Metro and draw their power from a central orb that is within the NILS Statue. These orbs power the rest of the Metro facilities, allowing for lighting, heating or cooling, and CQ Card and CQ-80 services.
Without power, not a whole lot is possible from within the Metro. Train services are still available as they use their own generators, but only essential lights throughout the entire Metro are lit, making the entire facility very dark.
Most interestingly, while access to testing station platforms are still possible, there is no way to enter the stations proper, as CQ services are not available.
The strange dreamlike visuals that usually surround the stations are not here - instead, every room and platform is simply surrounded by brick walls, rock, and concrete in the shape of the station layout. The Metro itself exists, though the views outside the train are much more boring.