Register SIP1 to the PBX and SIP2 to My2n

Create a Directory User for the My2n Mobile Devices

Create Automation based upon CallStateChange > Call Answered, Where CallerID is the incoming phone number, If the phone number is dynamic and you want all calls coming from SIP1 to be forwarded to the My2n App, you can miniplate the outbound caller ID on the PBX

Action is EndCall and another Action is initiate Call to User in Directory