For my travel date (8/17), there is no direct train between Milan and Domodossola due to track work. There are direct buses or train to Arona + bus to Domodossola.
I'm looking at the 2PM - 4:20PM direct bus, or 3:25PM - 5:55PM train + bus on Trenitalia. The 2PM bus would be great but I'm not sure I can make it due to a 12:30 lunch reservation in Navigli. It looks like the direct buses are bookable and do sell out sometimes, but the train + bus are not bookable, ie, can always get on like a commuter train?
The timetable allots only 5 minutes for the transfer in Arona. Do the replacement buses wait for all passengers to arrive in case of train delay etc? They must need a lot of buses to replace a train load of passengers.