OK you hit what I was asking. The very last part is what I am having issues with. To a person on the earth, the trains are moving at the same speed and have the same energy because they are moving with the earth. To an outside observer who is not on Earth - they are moving at different speeds...
You have two trains sitting on the equator (one on each side of the equator so they don't collide -.-). Train one is moving East with the rotation of the earth, train two in moving west against it. both trains accelerate to a speed close to the speed of light, using the same amount of energy. So...