Hello,

This is question on PBX behavior, what is the right thing to do, and how do PBX's generally behave. 

If a user on a phone, dials a number, which happens to be configured on the same phone system (for example another tenant), there are two options:
  1. The PBX notices this, and directly connects the phone to the DID on that system (breaking separation of tenants)
  2. The PBX sends the call out on the SIP trunk, and the provider-routing sends the call back as an incoming call.
What are the pros and cons of each option from the SIP provider point of view? 
How do PBX's generally behave? 

Thanks,
Antonio

PS: I reposted, because the original question was apparently not phrased in a clear way.