I'd be inclined to agree with the year round thing simply because of all the stuff there is involved in it. I vaguely recall Japanese schools did half day's on Saturday's back when the shadowrun realm split off then you have all the after school clubs, summer schools to catch up, camps and training for various clubs, staff meetings and education (although that'd probably apply less to a bus driver), things like the Jukans providing extra education (which in shadowrun would probably be corp run for its kids don't want them exposed to another corps education practices), extra classes in addition to the regular ones for things like the mage track, longer hours (meaning fewer holiday's or time off) because there's simply more content the kids have to learn if they're going to be viable employee's at least at the upper level where you probably would be providing a bus driver.
I can easily see 20 hours a week being reasonable as an all round figure since there'd probably be times you'd have to spend entire day's on the job e.g. your driving the insert Club X up to the mountains for their special training camp and that's assuming you'll only dropping off and picking up not actually spending the week up there with them.
