I'm certainly no expert on CME's but I do know that Quebec's power grid failure back in 1989, blamed on a powerful CME, occurred in the middle of the night. So, based on that, I would think, yes, a CME can also affect the night side of the Earth.

In Quebec's case, I suspect that it's location in more northern latitudes had something to do with its being knocked out of commision. However, with any CME powerful enough, I would think that higher latitudes near both poles, both day and night side, would be most at risk from the accumulation of charged plasma particles in the earth's magnetic fields.