Sharing a file with multiples shared channels

We're looking toward shared channels as a way to make everyone's life easier: no more tenant switching and no more guest accounts management.

I'm wondering if there is a way to allow collaboration between multiple shared channels For example, Team A and Team B would both have a shared channel with their own files, but would sometimes need to work together.

With O365 groups, we could grant access to a folder for a whole team. For example, we would host a folder in Team A SharePoint and gives access to Team B using the O365 group. We could also create a calendar event in Outlook and invite both team A and B for a joint meeting. But I've read that shared channels don't come with O365 group so I'm wondering how we would do something similar with shared channels. 

Is it possible for different teams using shared channels to collaborate together or are teams using shared channels doomed to work in silo? What would be the best (safest and easiest) way to make two teams using shared channels collaborate together on files and create joint calendar meetings?