I see. Well I still don't know what interfaces your monitoring system needs access to, but I assume it's SNMP polling and traps.
As I mentioned before, part of the information is available by polling (querying) the dashboard:
https://documentation.meraki.com/zGeneral_Administration/Monitoring_and_Reporting/SNMP_Overview_and_...
So for that part it doesn't matter where your access points are, you monitoring system will be querying the Meraki cloud.
For polling the other MIBs, your monitoring system needs access to the actual LAN IP addresses of the equipment you want to monitor. This is the case for all vendors. This access could be through routing, VPN tunnels, 1-to-1 NAT, portforwarding, some kind of SNMP proxy, ...
For traps it's the other way around, your devices need access to the LAN IP of the NMS. That access could be provided in a similar way.