AtD translation: not inseparable / dervish boys

[Mike Jing]

P843.36-844.3   Tough customers in from Constantinople on business sat at
tables in the back, smoking out of argilés, counting to themselves without
moving their lips, scanning every face that came and went. Their presence
(Cyprian was aware by way of Danilo) was not inseparable from the
activities of the Young Turkey Party and its Committee of Union and
Progress, headquartered here in Salonica. There were things these young
idealists needed in the way of matériel, parts of town that must be gone in
and out of without molestation, that only “dervish boys” knew how to help
with.

Why is it "not inseparable"? I'm not quite following the logic here.

Also, what are these "dervish boys" exactly?