In most cases, the electric operation with electro-diesels has been for limited speeds at short distances, not 110mph plus operation. But a bigger issue is that most high speed trainsets on the TGV plan are multiple-unit with power trucks under all coaches giving much higher total horsepower. This is what allows the roller-coaster 180mph operation on 4% grades. I would imagine you could conceivably build a diesel prime mover that could power equivalent multiple trucks in an articulated MU train, but the question is how big it would need to be.