Similar to a DMR repeater's 'Talk Groups',
The local MVMA PBX, nc8q-raspbx, has several 'Conferences'.
From a registered phone, if you dial 1093 you will be in 'talk group 1093'.
With the exception of PBXs are high-definition in multiple concurrent 'talk groups' and
DMR is low definition, one-at-a-time in 2 'talk groups' if the 'talk groups' are on different 'time slots'.

So, in a manner of speaking:

nc8q-pbx   has 'talk group' 1093 (937-1093)
w8bi-pbx   has 'talk group' 1193 (937-1193)
w8go-pbx   has 'talk group' 1493 (937-1493)
n2mh-pbx   has 'talk group' 2193 (973-2193)
k5glh-pbx  has 'talk group' 2093 (405-2093)
kd5tdk-pbx has 'talk group' 5193 (580-5193)

kd5tdk pbx and k5glh-pbx are automatically routing 6552 (OKLA) to the same 'talk group' 2093 starting a state wide 'talk group'.

Locally we (nc8q and w8go) could automatically route 6446 (OHIO) to w8bi-pbx's 1193 starting an Ohio state 'talk group'.

Just thinking out loud.

73, Chuck