В последних патчах появилась интересная фича, которая пока отсутствует в документации, но есть в менеджменте:
Call Routing Group (CRG) :
Description: As of version J1.410.38.c, OmniPCX Enterprise allows to program on a set an
overflow path instead of a unique number. This overflow path is defined as a list of numbers. When
an incoming call on a set overflows on the path, it rings these numbers one after the other, until the
call is taken or reaches the end of the list. If end of the list is reached, the incoming call overflows on
the voice mail of the set where the overflow path has been programmed.
On user’s set, overflow to a call routing group is defined as a forward. All types of forward are
allowed (immediate, busy, non-answer or busy & non-answer).
Restrictions: No CSTA transfer and No RSI for this feature

Limits: As call routing groups and entities share the same memory space, it is important to note that
this reference is common between the two objects. It means that if an entity with number 10 already
exists it will not be possible to create a call routing group with the number 10.
The limit of 4000 entries in the data base applies to the sum of entities and call routing groups.


Management is under “Group/Call Routing Group“

Node Number (reserved) : 1  
Routing Group Number : 1
Name : ----------------  
UTF-8 Name : ---------------------------------------  
Calls Distribution
1st Extension Routing : --------
2nd Extension Routing : --------
3rd Extension Routing : --------
4th Extension Routing : --------
5th Extension Routing : --------
6th Extension Routing : --------
7th Extension Routing : --------
8th Extension Routing : --------
9th Extension Routing : --------
10th Extension Routing : --------
11th Extension Routing : --------
12th Extension Routing : --------
Parameters
Overflow Timer : 0
Overflow on voice mail + Yes