Anons, I think this is where the FIVE EYE connection comes into play. An anon posted this tweet by Kim Strassel in bread #11744. Strassel opines over how the unmaskers knew which intel reports would have Genl. Flynn in them. Did they unmask every report they received in the hope of finding Flynn, or did they have a way of knowing which masked names would be Flynn.

The other FIVE EYE IC groups could have investigations up on the same targets, such as Ambassador Kislyak, but their reports would mask their own citizens (if they have that requirement), not US citizens. The other groups would feed back to the Obama admin which calls and dates had Flynn on them, or other Trump associates. Maybe they even targeted Flynn and Trump associates directly.