In 1950 the population of Hawiye from the outskirts of Mogadishu to Galkacyo was double that of MJ, so my grandfather slept with a shotgun while living as far north as Burtinle. Today MJ is as big as the Hawiye outside of Mogadishu, and they bring us their criminals to prosecute.
There was no war, no decisive battle. The HG have simply stopped any attempt at a military solution to the problem of Mudug. They got a sense that MJ was now a significantly larger clan and adjusted their behavior.
Something similar to this has already taken place in Hawd between the Ogaden and Isaaq. The Isaaq have gotten a sense that the Ogaden are now much larger than they are, so they have slowly pulled back north over the past 30 years. Away from Danood into Gaashaamo, away from Awaare to Daroor.
When the Dhulbahante are larger than Habar Magadle, you won't want to go to war.