You can direct bury USE cable. You're going to need more than what I would consider a hand hole box to splice them, and maintain proper bending radius.
Anyone who has moved a service like this, I would be interested in learning how exactly this is accomplished... I've never seen rmc threaded once it's already in the ground, or with wire in it. Does one cut the existing service ~ 5 ft closer to the utility, then cut roughly five foot of conduit off to have working length with the existing conductors? Or is the whole thing repulled as one solid run? How big of a trench would this typically require for the above posters scenario