If it has indeed been in place since WWII, who says it wasn't perfectly legal back then? And if so, the fact it's still hanging on says a lot. How many of today's conduit supports (listed or not) do you think will still be sound in 60 years?
A lot of the old stuff still works better than the new stuff anyway. Ask some of the POCO guys about transformers, for instance.
At least they used compression fittings below the plumbing pipe (wet location if I have seen one!), and I think that this is the first time I have seen a picture of knob and tube with EMT in the same shot. Is that romex branching off the knob and tube in the last pic? That is what I am used to seeing when people tap off of knob and tube. Code acceptable or not, i've seen it before.