Filter Users per Site Based on Custom Meta Data

Is it possible to be selective about the syncing of users?

We have one WP site that holds all our users. Could we sync to sub sites only if a user was in a given BuddyPress group or had a certain custom meta value assigned?

Eg if main is ticked in a users custom meta, they get synced to our main website. If someone has sub1 and sub 2 ticked then they get synced to sub site 1 and 2 but not to our main website?