After re-enabling VI Peak 15, Mira, in Mass Effect Legendary Edition, you will have the task of reconnecting various landlines across stations. You will have to reconnect these landlines to turn the train on again to get to the other part of the facility and get to Matriarch Benezia.
How to reconnect landlines
You will need to gain access to the roof of the building just behind Mira Core. All you have to do is turn around and go up the elevator.
When you get to the roof, there will be several Rachni soldiers and workers protecting this division. You will have to take them out. Your primary concern will be stronger because their poison can rupture your shields and damage your health over time, which can be very difficult to deal with depending on the difficulty you play. After they are taken care of, go to the main terminal of the area and activate the landlines.
The next step to activate the train to reach the other side of the peak 15 is to repair the reactor. You must return to Mira Core to get to it.
How to complete the reactor repair
When you get to the core of Mira, you want to go down the left corridor. Before you get there, the soldier Rachni will appear on the grate, you will have to remove him and then you can continue. The elevator to the reactor will take you downstairs.
When you reach the bottom of the reactor, it is likely that your sensors will be jammed. Instead of negotiating with Rachni, you will have to take down some Geth protecting the reactor. There are several Geth Destroyers and Stalkers bouncing around the walls. On the top floor will be Geth Juggernaut providing an overwatch for these enemies. We recommend removing everything right at the entrance and then dealing with Juggernaut last.
Then make your way to the center of the reactor core and you will be able to repair and reconnect the reactor lines.
Once you complete both of these tasks, the Peak 15 fixes will be completed. Now you can take the train and hunt Benezia.