Hello, I also use that firmware version, 2.1.5 build 200904.
Please let me know if you are going to upgrade.
Regarding your question, I use this, seems to be the same 
- platform: rest
name: Interfon Status
authentication: digest
username: admin
password: admin
scan_interval: 1
resource: http://192.168.1.xxx/ISAPI/VideoIntercom/callStatus?format=json
value_template: "{{ value_json.CallStatus.status }}"
You use the wireless connection on the intercom?
I have the wireless model but it is connected through Ethernet (POE). In the meantime seems like the snapshots are working better since I’ve changed the order of the actions in the automation.
I plan to do the upgrade soon however and because I have both the kv6113 for the inside door and the kv8113 for the street door i will try first on the kv6113 to see how it goes and let you know the result.
Also work for Hik Vision DS-KH6310-W. 
Hi guys, one question, does this integration works with indoor unit managing the doorbell? I read that the android units were bad, but the new ones seem a bit better, what do you think?
They are still bad and slow 