Provavelmente não são muitos
O Apêndice A nos diz que as Montanhas Cinzentas foram colonizadas por Thorin I, bisavô de Thorin Oakenshield, após a perda de Moria (ênfase minha):
[T]he glory of Moria passed, and its people were destroyed or fled far away.
Most of these that escaped made their way into the North, and Thráin I, Náin's son, came to Erebor, the Lonely Mountain, near the eastern eaves of Mirkwood, and there he began new works, and became King under the Mountain. In Erebor he found the great jewel, the Arkenstone, Heart of the Mountain. But Thorin I his son removed and went into the far North to the Grey Mountains, where most of Durin's folk were now gathering; for those mountains were rich and little explored.
Return of the King Appendix A "Annals of the Kings and Rulers" III "Durin's Folk"
No entanto, também nos dizem que esses assentamentos foram substancialmente abandonados após serem atacados por dragões:
But there were dragons in the wastes beyond; and after many years they became strong again and multiplied, and they made war on the Dwarves, and plundered their works. At last Dáin I, together with Frór his second son, was slain at the door of his hall by a great cold-drake.
Not long after most of Durin's Folk abandoned the Grey Mountains.
Return of the King Appendix A "Annals of the Kings and Rulers" III "Durin's Folk"
Todos esses eventos acontecem muito antes dos eventos de O Hobbit ; O Apêndice B nos diz que a morte de Dáin ocorre no TA 2589, enquanto a Quest for Erebor ocorre no TA 2941.
Como o texto acima diz apenas que as Montanhas Cinzentas foram abandonadas por "a maioria" do povo de Durin, supostamente pretendemos entender que alguns redutos permaneceram, mesmo 400 anos depois do fato.