Hi terx, it’s quite an interesting game and I’m no expert. I have noticed and read around about the way people in your cities “think”. If the total time for the trip takes more than 20 minutes, they will most likely just not take the trip. That said, if the distance between cities is great enough, your trams will not be able to breach this time barrier. So, trams will work great for inter-city trip if the cities are close. Once the gap widens, you run into the time barrier and must use higher speed vehicles.
Regarding the train maintenance cost, it can be prohibitive later on in the game. So far, my strategy has been to get a train line as quickly as I can. So, I pick 2-3 cities that are close to each other (preferably in a straigh line). I quickly build road infrastructure in all three cities to get the people moving. Once I’m profitable and my loans are paid off (usually within 10 years), I start building the first train line. It will lose money at first, but once it gets established, your citizens will fill the train stations.