Greetings from the North Country...
RS, I agree that it's not likely that the species in Utiger et al.'s study are more closely related to any other genera, but I have some reasons why I'm very tempted to go along with their new taxonomic changes to the old Elaphe genus.
First, I would say it's not hard for me to work with all the new names. I'm used to memorizing scientific names.
Second, it actually helps clear up understandings for me about the different species and how they evolved. For instance, I have always suspected E. longissima, etc., were very different from E. quatuorlineata, etc, and were a part of a different radiation. I've never thought they had the same ancestor as the other Elaphe that radiated north and east in Asia. Thus, some new genera, like Zamenis, are easily accepted by me.
E. mandarina is even more distant from the modern Elaphe, and even though they might have the same archaic ancestor, this species is very different from the typical Elaphe. I think the new genus name reflects the distance and the individuality of the species in Euprepiophis. So, a third reason is how different a group is from the other Elaphe.
When it finally comes to taeniura/moellendorffi, etc, of the new Orthriophis, I would leave them in the Elaphe, except for the fact that E. scalaris has already been removed and put in the genus, Rhinechis. It would be kind of inconsistent to leave older species in the Elaphe. But I could change my mind here, and continue to call taeniura, and others in this group, Elaphe. The fourth reason, then, would be to keep consistency.
Finally, my last reason has to do with the fact that the New World ratsnakes, the Lampropeltini, are quite different from the Old World Elaphe. The species in Pantherophis are closely related, and although they're fairly close to the ratsnakes of the Old World, the new Elaphe, they are separated by lots of time and space. In Utiger et al.'s opinion, enough to create a new genus.
So, there's a few reasons why I'm vacillating on this subject. What we do here is an important subject area. Too bad we can't know about all the ancestors of the various modern ratsnakes. At one time there may have been only one species that covered all of Laurasia and inhabited the Arcto-Tertiary geoflora, but I doubt that, since the ratsnakes are so good at diversifying and occupying so many microhabitats today. Just look how many species we have. I think there's a good chance that more than one species of ratsnake made it into North America way back in the early Miocene. Also, I believe there were most likely several ancestors for the various ratsnake species that Utiger et al. are dealing with. I think keeping all the old Elaphe species in the Elaphe would be saying that they all have a common ancestor and also that they are all a lot alike, which doesn't seem to be true to me.