Yes. In 1.0.1 beta, we added an option for external tunnel concentrator. This Knowledge Base article has more details:
To any router supporting standard IPv6 L2 GRE. i.e, protocol 0x6558, transparent ethernet bridging. I think Microtik supports proprietary EoIPv6 tunnels, not standard IPv6 GRE
GRE can carry the VLAN traffic. Not sure I am answering the question.
As described in the user guide:
L2 bridge employs Ethernet over GRE (EoGRE) to carry the customer traffic across the Terragraph network.
when L2 bridge is enabled, all CNs and DNs will automatically create a EoGRE tunnel with their POP node and the POP node will create a tunnel back to each of those CNs/DNs. The tunnel is capable of carrying both IPv4 and IPv6 customer traffic between CN and POP. Where the IPv6 over tunnel can be optionally disabled from the UI.
All tunnels at the PoP get bridged. In Release 1.1, we will introduce VLAN trunk ports.