Ausgrid installs its first power pole-mounted batteries in NSW

I don't think this is blackout redundancy, that would be more complicated and expensive to implement compared to just a grid-tied inverter + battery.

For this to work during blackouts it would need a very large inverter so that it can supply the entire draw of many (how many?) houses without browning out. I don't think you could fit such a thing up poles unless you install one every few poles and do lots of rewiring.

The article only makes one claim about the operation mode of the batteries:

“They can store excess energy generated during periods of high production and release it during times of low production or high demand."

At a guess: they're probably monitoring the line voltage and just choosing whether or not to input or output. At times of high demand (typically evenings) the 240V droops a bit low and they would start outputting to the grid. At times of high local solar supply (sunny midday) the 240V rises high and they would probably charge the battery.

Have a read about "solar voltage rise" for more info. Lots of home grid-tied solar installs have to limit their output during midday because the local network line voltage goes too high and risks blowing up appliances.

Trying to co-ordinate thousands of distributed systems like this is nigh impossible.

They (within limits) wouldn't need to if they used the method I detail above.

...if they installed lots of these nearby to each other then they'd have to do some modelling of the control algorithms to make sure they're stable. I'm sure someone will stuff that up at some point in order to optimise aggressiveness of charge/discharge ($ earned/saved) instead, leading to some fun news stories.