Not sysadmin specifically, but when I was working as a computer technician, questions we would ask to scope out the skills of people were along the lines of:
Q: "Something you have no experience with has broken and won't do a basic function, how will you go about fixing it?"
A: Research, ask someone else etc.
Q: "X is missing their password for a system we have no admin rights on. How are you going to fix this?"
A: Recovery Tools. Format device and set it up again. Use JS/Developer tools to get it in plain text from the browser.
I haven't experienced FTTH yet, but reports from people who do have it seem really good.
I have however worked supporting both FTTP and FTTH on a private network. In my experience, FTTH was so much simpler to diagnose. If there was an issue you would check the exchange, and their house. The Fiber converters we had where tiny compared to the ones NBNCo offers too.
The FTTN users where a lot harder to deal with. All the network equipment is still fairly young (under 10 years iirc), but we would still get cables from the pits that needed to be rerun. Our nodes supported 4 houses at most. Though most of them only had 1 or 2 users attached to them.
I am up for this. I've been working on Admin Job Log (http://www.adminjoblog.com) on and off for just over a year now. Having someone else trying to get a product out would be great motivation.