Its internally drilled for the di2 junction on both sides of the bars so you can feed the cable into the hole on the right and all the way through to the left and the junction box. The brake cables are external but you can run that Di2 cable internally. Thats the only Di2 cable that would be internal. The ones from left bar end to shifter and left shifter to the frame would be under the tape.
Emailed wiggle to be sure and they said that there is no internal routing on the x-light so that arrangement isn't possible. Maybe worth going for those aeroz ones which apparently can be routed fully internally.
Its internally drilled for the di2 junction on both sides of the bars so you can feed the cable into the hole on the right and all the way through to the left and the junction box. The brake cables are external but you can run that Di2 cable internally. Thats the only Di2 cable that would be internal. The ones from left bar end to shifter and left shifter to the frame would be under the tape.