The "But Google" rebuttal: I was in a city when they had a public transport strike. The buses/trams would run at irregular times, but as far as Google knew (maybe the public transport company told them so), no buses would run at all.

So trying to get anywhere, Google Maps would say "Walk 20 minutes to the nearest train station, take the train, walk 15 minutes to your final destination.". I had to trick it and say I want to depart 6 months in the future so it would show which tram/bus-lines I actually need, where I can go to the stop and take a chance that one would show up..

If the bus never goes on a Sunday, it should be possible to record that in the opening_hours according to the Public Transport v2 scheme: https://wiki.openstreetmap.org/wiki/Public_transport Still not real-time, but better than nothing.