Yes, more Poles than Danes IIRC, which given Iceland's history is quite the feat. Similar to the UK, Polish workers occupy a lot of the builders/drivers/cleaners type blue collar positions in the economy.
Of course, Iceland has a total population of a mid-sized city, so we're talking ~21k Polish people compared to ~4k Danes.
I had to call an attendant up to understand how in the word to turn the shower on (there was a long skinny faucet the water poured into the tub that had to be turned clockwise) which she said she was confused by it too and had someone show her. It was in an older Icelandic hotel that used their natural hot water (sulphur stinky but i didnt mind) from the ground for showering or any type of hot water use.
Depending on where in the city you are, that is the hot water you get. The age of each building has nothing to do with it.
Tom Scott has a small video on it: https://piped.kavin.rocks/watch?v=OgMXjAQ5q14