The way you are putting it is a bit like saying that the average time between eating breakfast and being struck by lightning is only 12 hours, so don't eat breakfast!
I don't think that eating breakfast is a precursor to being hit by lightning whereas stopping on a montorway is certainly a precursor to being involved in a rear end collision. This is why whenever I take a school group on a motorway I inform the teachers what will be done should the coach break down - it's unlikely but it is a significant risk factor. Unless your cereal is particularly rich in iron, that is, then feel free to be concerned by all sources of high voltage electricity.
Don't be silly this isn't trent barton!
My take on this as someone employed in a bus/coach company:
Breakdowns do happen, they are fairly unavoidable, so many companies do have a policy in place. Often the solution used is that a second vehicle from the same company will collect the passengers, with both drivers assisting in the transfer.
Bearing in mind that buses do carry a number of vulnerable passengers there is good reason for caution to be exercised. School children for example are not as worldly wise, nor do they often follow instructions as well, so keeping them aboard the vehicle is pretty reasonable. The infirm may struggle to alight from the vehicle to the road and so keeping them on board (and sheltered) until another driver/support staff arrive to assist is also preferable. Likewise partially sighted people may struggle to perceive hazards when alighting away from a lit and level paved bus stop, or the elderly may not be as aware of traffic or the surroundings. When alighting onto the pavement at a bus stop it is accepted and understood it is a safe environment, one which they feel is an acceptable level of risk - they must have used to it board the bus. However a broken down vehicle in an unusual place adds another element of risk to it, one which the passengers did not necessarily suspect would happen - so the company/driver needs to take
reasonable steps to prevent them from potential danger.
Also from a sudden breakdown a driver may not have enough time to align suitable with the curb, today for example I picked up passengers in a minicoach at a bus stop designed for level boarding of low floor buses. My door's first step was at a similar level to the curb but was around 6 inches away as it swings outwards and the paving slopes stopping me getting nearer. This gives an example of the risk of minor injuries possible to an able bodied person during an abnormal alighting situation, but also an example of making a judgement and common sense prevailing: I made the passengers aware of the hazard and assisted them on boarding.
In my opinion this incident has been blown out of proportion, it was bad PR and not very customer focussed. However without any exact details we cannot comment with any reasonable accuracy, but if the driver made the decision it was not safe to alight/wait/walk in that position and chose to wait for a second staff member and a bus as close as possible was it such a bad thing to do? Likewise with evacuation, from the descriptions given it sounds like somewhere the bus was reasonably safe to be stopped but not necesarily the safest place for passengers to be disgorged to. The questions I would ask myself if I was the driver: "Is it unsafe to be stopped here?"/"Would I find it acceptable to be stopped here under normal circumstances?" (safe - do not evacuate), "Is it unsafe to alight here?"/"Would I find it acceptable to alight here under normal circumstances?" (possibly unsafe - further assess/await back-up).
We'll probably never know much about it and given the level of hyperbole I'm taking the OP's comments with a pinch of salt. Ultimately most companies do have a similar policy: keep passengers on the bus and wait for another vehicle, so other than taking slightly longer than desirable I don't see why this is any worse than any of the other tens of break-downs that happened across the country today. Not great...but not a hostage situation either!
As a side note - that's my uni exams done for this year and a whole week of 10-12 hour days at work finished. So as you can see I now have time on my hands I haven't had recently to read long threads and reply!