Real-world current use of frequencies.txt?

[Charles_Belov_SFMTA]

Is there an agency currently using the frequencies.txt GTFS Schedule file to describe service on a route that has both headway-based and schedule-based service.

San Francisco International Airport uses frequencies.txt, but two routes are exclusively headway-based and their other two routes are exclusively schedule-based.

I'm talking about where a single (or more) route(s) have both headway-based and schedule-based service in a single route.

Apparently STM (Montreal) used to use headway-based, but now their GTFS data is exclusively schedule-based.

Charles Belov

San Francisco Municipal Transportation Agency