This information from the document is key
VLAN tags are not maintained across wireless mesh links, any VLAN tags applied by wired infrastructure will be stripped before sent across the air.
For the above reason, you need a device that will present all traffic to the mesh AP as untagged. This is achieved by a MX NATing the traffic of potentially multiple VLANs and presenting it as untagged VLAN 1, as shown in the article linked
https://documentation.meraki.com/MR/WiFi_Basics_and_Best_Practices/Extending_the_LAN_with_a_Wireless...
So this presents the problem of managing multiple VLANs in building B. The MS range does not have this NAT capability so the short answer to your question is no, this cannot be achieved.
I would speak to your Meraki Sales representative and there Design engineer who will be able to look at workable alternatives.