Briefly, if you check the steam engines directly above the player (bottom row of generators), the middle one says "Water temperature: 100" but "Performance" and "Available performance" both 0. See also the steam engine to the right of that one, which has been broken and replaced and is reporting water temperature of 0.
Further note the row above those, which has steam engines reporting water temperature 15.
http://www.narc.ro/tmp/bugreport-steam.zip
This design of powerplant has otherwise worked fine for me in the past -- four boilers are enough to fully heat three steam engines and provide enough excess heat for pipe transport; what I've changed from previous unbugged cases is that there are now underground pipes between the boilers and steam engines, feeding directly to the steam engines. I have no idea if that's causing the oddity, but it seems a likely enough culprit.
...in fact, since I thought of that, I just checked: if you break the underground pipes linking the three inactive rows of steam engines (top three rows, in other words), the bottom two rows start working as expected; replacing the underground pipes will eventually trigger the bug again (took about 1 minute or so to show up for me).
