(a) is fixed because there's probably no-one for the Texan to talk to on the bus. For trains, the person to talk to is on the platform, and can simply let the train depart (example: Copenhagen Metro, although good luck spotting any staff).

It could be more easily fixed by accepting foreign credit cards (Gothenburg manages this, London if the card is contactless) or telling drivers not to wait.

(b) is partly solved if the cost of running buses/trains is significantly reduced, as that leaves money for extra vehicles.

(c)... well, who will notice?

Also, regarding (b):

Already many cities today operate busses by taking unemployed people and forcing them to take the job as bus driver for no pay (they'd have to continue living off of welfare), otherwise they'd lose 50% of their welfare money.

That's how you get bus drivers for free — automated vehicles can't really beat that.

I think that this amounts to a small pebble in the mountain of technologies that have to be developed to enable AVs.

Here's an easy solution: every bus stop has a kiosk that dispenses a RFID bus pass if you put in your payment info. Then, when the bus comes, you can enter from any door and the RFID receivers detect your presence. Attempts to board without a bus pass are detected with weight sensors and a camera network (current computer vision techniques are probably reliable enough for this application; they'll be even better in a few years). Unauthorized persons are advised to get off at the next stop by audio recording and identified by displaying a snapshot of their face (taken earlier on the bus). If they don't get off the transit police are summoned.

Fix with POP (Proof-of-Purchase). That is, you can enter the vehicle through any door, but you must have a valid ticket. Occasional inspectors check the tickets, and issue fines for people who don't have tickets such that the expected cost of not paying your fare is on the same order or lower than fare beating.

Put a fare vending machine which accepts cash and credits cards on the bus, which also makes it very obvious how to get a single fare. (This exists for example for trams in Berlin, modulo the accepting credit cards part)

We’re currently in the process of switching to RFID-cards as tickets, and allowing people with RFID credit cards to also pay via those.

But yes, all these issues are solveable – but "how close does the bus operate to the schedule" usually is not related to who drives it, but to how these issues are solved.

In fairness, I think the best way to fix (a), (b) and (c) would actually be by automated buses or trains, that would enforce reasonable limitations strictly, without the possibility of negotiation.

i.e. the passenger would be prevented from boarding the vehicle without a valid ticket and provided there was sufficient capacity for a speedy and comfortable boarding.