Actually outside there are more than four Toshiba units, there are five!

Let's assume that all of our indoor units are connected to the separate units, why would all four indoor units go down at once (with remotes all displaying the same error)? Or is it possible to spread the cooling load across several compressors in the same system? (that's me guessing)

They do seem to be all part of the same installation - see the shared insulation in this picture:
https://drive.google.com/file/d/0Bz_...ZVzZzeUVn/view

Each is attached to switch looking like this, I tried moving it there and back but no sound could be heard from any compressor (although one of them started leaking water from the hose, but maybe it was just a coincidence). I'm guessing this is where the fuses are. Maybe I should just replace all the fuses just in case since it was part of a power surge (the outage).

https://drive.google.com/file/d/0Bz_...wWnJ5MjMw/view

Engineers wouldn't be able to take out the cassette indoor units (that would require cutting through the fake wooden walls that are hiding the units), but they can peak inside through the vents. I took some pictures through them, there is some copper piping visible but nothing stands out to me.

https://drive.google.com/file/d/0Bz_...WakhhWkZJ/view
https://drive.google.com/file/d/0Bz_...5ZjBqWUJj/view