Meeeeh, my ISP cut of around 100+ fiber connections in my town and spend three weeks fixing it. My neighbor have business line, there's an SLA on those that among other things, require them if reestablish his connection within 3 - 5 hours. It took them over 500 hours, so that SLA is useless for anything but forcing compensations.

The problem is that the SLA should give an indication of available resources, but in reality it's mostly a contractual thing for most companies, they'll pay the "fine" or refund a customer if they fail to hit their SLA and that's about it. Tarsnap most likely have better availability than many midsize competitors simply because it's just one person who really cares about it. Doesn't help if he's hit by a bus though.