Possible to create separate VLAN or access SMB between 2 connections of same ISP who's using CGNAT?

Shimla, India
I have a question/curiosity on whether this can work and it might be helpful.
So we have a local ISP providing FTTH connections.
I and my friend live in same locality (around 800 meters apart) We both plan to get connection from this ISP and was thinking if it's possible to access each other's LAN on gigabit speeds?(ONT are gigabit from Genexis and OLT are most probably gigabit as well) We also think that we might be connected to same OLT in the area.

So will it be possible for us to share resources on LAN speed and not use internet bandwidth (20Mbps plan) for sharing data between us.

The ISP uses CGNAT so they assign ip from 172.x.x.x or 10.x.x.x range to the subscribers and also assign VLAN to users.
Bangalore | Ernakulam
Excitel | BSNL
It would also depend on how they have setup the network, you may not be able to directly reach the other customers even if they are part of the same network or VLAN.

You could also ask the local ISP, if they can setup a different VLAN just for you guys which doesn't have internet access, but where the local traffic is allowed. Then use ZeroTier for the added security.