The claim is that IPSec core networks can be subjected to a denial of service, and that this will result in a DoS for the users. That's correct but not very interesting.
The researchers then go on to note that a DoS on 4G specifically can put users into a vulnerable position by shoving them over onto 2G networks, which are very vulnerable. But at the end of the day it's still only a DoS on LTE-- what you've switched to after that is not LTE's problem.
That's not to say the LTE isn't vulnerable, of course. Breaking data plane crypto at the ENB means that limited physical penetrations convert them into very effective surveillance tools. And the data plane crypto isn't great (lacks integrity protection). I've suspected in the cold quiet of my heart that some operators run EIA0 in production. Etc.
So, yay for DoS, but I wish people would use the word "hacked" a bit more clearly, or drop it all together.