You're right, bus drivers should get more than train drivers, heck maybe they should get more than airline pilots.and battle constant traffic, you cannot relax for a second, behind the wheel. Even when at the bus stops, they are dealing with fares, passengers, and their needs. Worth treble what they pay train drivers, able to relax and almost fall asleep in the cab - they even have/need equipment fitted, to remind them to stay awake.
Sorry, on almost no level can bus driving be equated to being responsible for a passenger train.