You can easily manage IP Intercoms and Access Units with 2N Access Commander over internet.
Since every 2N IP product including 2N Access Commander behaves like any standard IP device, you can use standard network techniques for interconnecting them over Internet.
Most popular techniques how to interconnect 2 separated sites over internet are:
NAT and PORT Forwarding technique
Since connection is established from Access Commander to each 2N IP device, you need to make sure that all 2N IP devices are reachable over internet. In standard environment, such 2N IP devices will have private IP address and only one shared IP address actually reachable from internet.
In order to allow communication from internet to each such 2N IP device which has its own private IP address, you need to use NAT / Port forwarding on site with 2N IP devices (SITE B and ROUTER B on image below).
Each 2N IP device listens on port 443 for incoming connection.
You do not need to perform such action on SITE A, just make sure that Access Commander is allowed to access internet.
With its specific implementation on your sites, any Network company/administrator will be able to help you.